[Mulgara-svn] r147 - trunk/docs/oldSite
thomas at mulgara.org
thomas at mulgara.org
Fri Dec 8 00:09:00 UTC 2006
Author: thomas
Date: 2006-12-07 18:08:59 -0600 (Thu, 07 Dec 2006)
New Revision: 147
Added:
trunk/docs/oldSite/187.htm.mine
trunk/docs/oldSite/187.htm.r139
trunk/docs/oldSite/187.htm.r91
Log:
added some accidently deleted stuff to the oldSite backup
Added: trunk/docs/oldSite/187.htm.mine
===================================================================
--- trunk/docs/oldSite/187.htm.mine 2006-12-08 00:07:07 UTC (rev 146)
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+
+<docsmeta>
+<title> select </title>
+<link rel="icon" type="text/png"
+href="./media/images/icons/siteicon.png" />
+<link rel="shortcut icon" type="text/png" href="siteicon.png" />
+
+<meta name="author" content="Tom Adams" />
+<meta name="copyright" content="Copyright © 2003, Kowari Project" />
+<meta name="robots" content="all" />
+<meta name="description" content="Mulgara Project Home" />
+<meta name="keywords" content="select, mulgara project, metadata, metastore, metadatabase, datastore, database, scaleable, scalable, transaction, java, open source,homepage" />
+<meta name="location" content="Global" />
+<meta name="document-distribution" content="Global" />
+
+<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
+<meta http-equiv="dialect" content="AU" />
+<meta http-equiv="language" content="English" />
+<meta http-equiv="window-target" content="_top" />
+
+<meta name="DC.Title" content="mulgara : semantic store" />
+<meta name="DC.Creator" content="Tom Adams" />
+<meta name="DC.Creator.Address" content="http://www.adams.id.au/tom/index.php" />
+<!--<meta name="DC.Contributor" content="Andrew Newman" />-->
+<meta name="DC.Subject" content="Mulgara Project Home" />
+<meta name="DC.Description" content="Mulgara Project Home" />
+<meta name="DC.Date.Created" scheme="iso8601" content="2003-09-22" />
+<meta name="DC.Modified" scheme="iso8601" content="2003-09-22" />
+<meta name="DC.Language" scheme="rfc1766" content="en" />
+<meta name="DC.Rights" scheme="URI" content="http://www.kowari.org/about/index.php#copyright" />
+<meta name="DC.Type" content="Text.Homepage.Personal" />
+<meta name="DC.Identifier" scheme="URI" content="http://mulgara.org/" />
+
+<meta name="Generator" content="AITPublish" />
+
+<link rel="stylesheet" href="mulgara_stylesheet.css">
+<!-- <link rel="stylesheet" href="44.css"> -->
+
+</docsmeta>
+
+<table border="0" width="100%">
+<tr valign="top">
+<td width="80%">
+<table cellpadding="0" cellspacing="0" border="0">
+<tr valign="top">
+<td width= "18">
+
+<p><a href="186.htm"><img src="previous.gif" alt="Previous Topic" height="25px" width="23px" vspace="2" hspace="2" align="bottom" border="0" /></a></p></td>
+<td width= "18">
+
+<p><a href="195.htm"><img src="next.gif" alt="Next Topic" height="25px" width="23px" vspace="2" hspace="2" align="bottom" border="0" /></a></p></td>
+</tr>
+</table>
+<h2>select</h2>
+
+<p>Issues queries to Mulgara servers and displays the corresponding results. The command consists of a sequence of <code><a id="h217" class="documentlinktemplate" title="select Clause" href="187.htm#o188">select</a></code>, <code><a id="h218" class="documentlinktemplate" title="from Clause" href="187.htm#o189">from</a></code>, and <code><a id="h206" class="documentlinktemplate" title="where Clause" href="187.htm#o197">where</a></code> clauses; and may optionally include <code><a id="h219" class="documentlinktemplate" title="order by Clause" href="187.htm#o190">order by</a></code>, <code><a id="h220" class="documentlinktemplate" title="offset Clause" href="187.htm#o192">offset</a></code> and <code><a id="h221" class="documentlinktemplate" title="limit Clause" href="187.htm#o191">limit</a></code> clauses. With all clauses present, the general syntax is as follows:</p>
+
+<p class="commandtext">select columns from models where constraints order by variables limit count offset count;</p>
+
+<p>The purpose of the <code>select</code> command is to find values for some set of variables that satisfy the specified constraints. All variable names start with a dollar sign (<code>$)</code>, for example <code>$x</code> or <code>$title</code>.</p>
+<table cellpadding="0" cellspacing="0" border="0">
+<tr valign="top">
+<td width= "226.8">
+
+<p class="relatedheading">In This Section</p>
+<p class="relateditem"><a href="187.htm#o188">select Clause</a></p>
+<p class="relateditem"><a href="187.htm#o189">from Clause</a></p>
+<p class="relateditem"><a href="187.htm#o197">where Clause</a></p>
+<p class="relateditem"><a href="187.htm#o190">order by Clause</a></p>
+<p class="relateditem"><a href="187.htm#o191">limit Clause</a></p>
+<p class="relateditem"><a href="187.htm#o192">offset Clause</a></p>
+<p class="relateditem"><a href="187.htm#o193">subquery Function</a></p>
+<p class="relateditem"><a href="187.htm#o194">count Function</a></p>
+<p class="relateditem"><a href="187.htm#o2776">having Clause</a></p></td>
+<td width= "226.8">
+
+<p class="relatedheading">See Also</p>
+<p class="relateditem"><a href="271.htm">iTQL Commands</a></p>
+<p class="relateditem"><a href="170.htm">alias</a></p>
+<p class="relateditem"><a href="171.htm">backup</a></p>
+<p class="relateditem"><a href="223.htm">comment (#)</a></p>
+<p class="relateditem"><a href="174.htm">commit</a></p>
+<p class="relateditem"><a href="176.htm">create</a></p>
+<p class="relateditem"><a href="178.htm">delete</a></p>
+<p class="relateditem"><a href="179.htm">drop</a></p>
+<p class="relateditem"><a href="180.htm">execute</a></p>
+<p class="relateditem"><a href="181.htm">help</a></p>
+<p class="relateditem"><a href="182.htm">insert</a></p>
+<p class="relateditem"><a href="183.htm">load</a></p>
+<p class="relateditem"><a href="184.htm">quit</a></p>
+<p class="relateditem"><a href="185.htm">restore</a></p>
+<p class="relateditem"><a href="186.htm">rollback</a></p>
+<p class="relateditem"><a href="195.htm">set</a></p></td>
+</tr>
+</table>
+
+<a name="o188"></a><h3>select Clause</h3>
+
+<p>Specifies the variables to solve for and their order in the result. For example:</p>
+
+<p class="commandtext">select $title $author $date ...</p>
+
+<p>Constant resource or literal values may be part of a <code>select</code> clause. In these cases, dummy variable names (<code>$k0</code>, <code>$k1</code>, <code>$k2</code>, … <code>$kn</code>) are created for the constant values.</p>
+
+<p>The following example returns three columns: <code>$k0</code>, <code>$x</code> and <code>$k1</code> where the values of <code>$k0</code> and <code>$k1</code> for every solution are the literal value <code>foo</code> and the resource value <code>http://www.site.domain.net</code> respectively.</p>
+
+<p class="commandtext">select 'foo' $x <http://www.site.domain.net> ...</p>
+<a name="o189"></a><h3>from Clause</h3>
+
+<p>Specifies the model to query. For example:</p>
+
+<p class="commandtext">... from <rmi://mysite.com/server1#model1> ...</p>
+
+<p>Because models are sets of statements, it is logical to compose them using set operations. The <code>from </code>clause permits set union using the <code>or</code> operator and set intersection using the <code>and</code> operator, with parentheses used to control association.</p>
+<a name="o3149"></a>
+
+<p>The following example queries only the statements appearing in all three models. </p>
+
+<p class="commandtext">... from <rmi://mysite.com/server1#model1> and <rmi://mysite.com/server1#model2><br />
+ and <rmi://mysite.com/server1#model3> ...</p>
+<a name="o197"></a><h3>where Clause</h3>
+
+<p>The <code>where</code> clause is usually the largest and most detailed clause of the <code><a id="h207" class="documentlinktemplate" title="select" href="187.htm">select</a></code> command. It specifies the constraints that must be satisfied by the variable values in each solution. A constraint is a sequence of subject, predicate and object that represents an RDF statement. Each of the three positions is either a constant value (a resource or a literal) or a variable. The Mulgara server finds values for any variables such that the resulting statement is present in the model that was specified in the preceding <code><a id="h1326" class="documentlinktemplate" title="from Clause" href="187.htm#o189">from</a></code> clause.</p>
+
+<p>For example, the following <code>where</code> clause constrains that in all solutions, the value of <code>$title</code> is the title of the resource referred to in <code>$document</code>.</p>
+
+<p class="commandtext">... where $document <dc:title> $title ...</p>
+
+<p>Constraints may be composed using <code>and</code> and <code>or</code> operations, with parentheses to control association.</p>
+
+<p>The following example returns every document with a title, an author and a subject of either botany or zoology. Documents without a known title or author are not returned.</p>
+
+<p class="commandtext">... where $document <dc:title> $title and $document <dc:creator> $author <br />
+ and ($document <dc:subject> 'botany' or $document <dc:subject> 'zoology') ...</p>
+<a name="o1530"></a><h4>in Specifier</h4>
+
+<p>Constraints may optionally contain an <code>in</code> specifier to resolve the constraint against the statements in a specified model, rather than the one specified in the <code><a id="h1303" class="documentlinktemplate" title="from Clause" href="187.htm#o189">from</a></code> clause.</p>
+
+<p>The following example constrains the result by titles in the <code>#books</code> model rather than the one specified in the <code>from</code> clause.</p>
+
+<p class="commandtext">... where $document <dc:title> $title in <rmi://mysite.com/server1#books> ...</p>
+<a name="o1531"></a><h4>Assigning a Value to a Variable (mulgara:is)</h4>
+
+<p>Constraints may also assign a value to a variable rather then querying for it. The special property <code>http://mulgara.org/mulgara#is </code>(or the aliased form <code><mulgara:is></code>) can be used with a variable as its subject and a non-variable value as its object. This assigns the non-variable value to the variable.</p>
+
+<p>The following example results in every document authored by Mendel about genetics, or by Mendeleev about chemistry.</p>
+
+<p class="commandtext">... where $document <dc:title> $title and $document <dc:creator> $author <br />
+ and $document <dc:subject> $subject <br />
+ and (($author <mulgara:is> 'Mendel' and $subject <mulgara:is> 'genetics' ) <br />
+ or ($author <mulgara:is> 'Mendeleev' and $subject <mulgara:is> 'chemistry')) ...</p>
+<a name="o1532"></a><h4>Traversing a Graph (walk Function)</h4>
+
+<p>Traversing a graph allows a query to return values, based on a predicate, by following up or down a hierarchy of statements. In a schema language such as RDFS, these hierarchies are expressed as a sub-class or sub-property predicate. Traversing a graph is performed with the <code>walk</code> function within a <code><a id="h1321" class="documentlinktemplate" title="where Clause" href="187.htm#o197">where</a></code> clause.</p>
+
+<p>The syntax of the <code>walk</code> function is either:</p>
+
+<p class="listcontinuecommandtext">walk ($subject_variable <predicate_URI> <object_URI> and<br />
+$subject_variable <predicate_URI> $object_variable)</p>
+
+<p class="listcontinue">or</p>
+
+<p class="listcontinuecommandtext">walk (<subject_URI> <predicate_URI> $object_variable and<br />
+$subject_variable <predicate_URI> $object_variable)</p>
+
+<p>The <code>walk</code> function must be bound to a <code><a id="h1298" class="documentlinktemplate" title="select Clause" href="187.htm#o188">select</a></code> clause using the same triple pattern that matches the second parameter. For example:</p>
+
+<p class="commandtext">select $subject <predicate_URI> $object<br />
+...<br />
+where walk ($subject <predicate_URI> <object_URI> and<br />
+$subject <predicate_URI> $object);</p>
+
+<p>An example of <code>walk</code> is demonstrated using the following statements:</p>
+
+<p class="commandtext">[ ( <kangroos>, <rdfs:subClassOf>, <marsupials> )<br />
+ ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br />
+ ( <placental-mammals>, <rdfs:subClassOf>, <mammals> )<br />
+ ( <mammals>, <rdfs:subClassOf>, <vertebrates> ) ]</p>
+
+<p>To query a set of statements in the hierarchy ending with <code><vertebrates></code> as an object:</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />
+...<br />
+where walk($subject <rdfs:subClassOf> <vertebrates><br />
+and $subject <rdfs:subClassOf> $object);</p>
+
+<p>Working from the bottom up, the system:</p>
+<ul><li>Matches <code>( <mammals>, <rdfs:subClassOf>, <vertebrates> )</code> and then substitutes <code><mammals></code> for <code><vertebrates></code> in the constraints.</li><li>Attempts to match for the triples <code>( *, <rdfs:subClassOf>, <mammals> )</code>.</li><li>Then matches for <code>( <marsupials>, <rdfs:subClassOf>, <mammals> )</code> and <code>( <placental-mammals>, <rdfs:subClassOf>, <mammals> )</code>.</li><li>Then matches for <code>( *, <rdfs:subClassOf>, <marsupials> )</code> and (<code> *, <rdfs:subClassOf>, <placental-mammals> )</code> and so on.</li></ul>
+<p>The result of the query is:</p>
+
+<p class="commandtext">[ ( <mammals>, <rdfs:subClassOf>, <vertebrates> )<br />
+ ( <placental-mammals>, <rdfs:subClassOf>, <mammals> )<br />
+ ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br />
+ ( <kangaroos>, <rdfs:subClassOf>, <marsupials> ) ]</p>
+
+<p>You can also traverse down the graph following the hierarchy. For example:</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />
+...<br />
+where walk(<kangaroos> <rdfs:subClassOf> $object<br />
+and $subject <rdfs:subClassOf> $object);</p>
+
+<p>This returns:</p>
+
+<p class="commandtext">[ ( <kangaroos>, <rdfs:subClassOf>, <marsupials> )<br />
+ ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br />
+ ( <mammals>, <rdfs:subClassOf>, <vertebrates> ) ]</p>
+<a name="o1535"></a><h4>Transitive Closure (trans Function)</h4>
+
+<p>Transitive closure provides the ability to express a function that generates new statements. Normally, transitive closure produces both existing and new statements. The <code>trans</code> function in iTQL<sup>TM</sup> only produces new statements, statements that did not exist in the model before it was executed. The <code>trans</code> function can be further constrained by limiting which statements are inferred and by giving it a starting or termination point.</p>
+
+<p>The simplest form of the <code>trans</code> function defines a predicate to operate on:</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />
+...<br />
+where trans($subject <rdfs:subClassOf> $object);</p>
+
+<p>This generates a new statement, <code>$x <rdfs:subClassOf> $z</code>, when it finds two statements that match the pattern <code>$x <rdfs:subClassOf> $y</code> and <code>$y <rdfs:subClassOf> $z</code>.</p>
+
+<p>For example, consider the following set of statements:</p>
+
+<p class="commandtext">[ (<mammals>, <rdfs:subClassOf>, <vertebrates>)<br />
+ (<eats-leaves>, <rdfs:subPropertyOf>, <herbivore>)<br />
+ (<marsupials>, <rdfs:subClassOf>, <mammals>)<br />
+ (<placental-mammals>, <rdfs:subClassOf>, <mammals>)<br />
+ (<elephants>, <rdfs:subClassOf>, <placental-mammals>)<br />
+ (<kangaroos>, <rdfs:subClassOf>, <marsupials>)<br />
+ (<red-kangaroos>, <rdfs:subClassOf>, <kangaroos>) ]</p>
+
+<p>As a tree it looks as follows:</p>
+
+<p><img src="1536.gif" alt="Transitive Closure" height="273" width="252" vspace="0" hspace="0" align="bottom" border="0" /></p>
+
+<p>Based on the constraint in the query, the first and third statements match the pattern <code>(<marsupials>, <rdfs:subClassOf>, <mammals>) and (<mammals>, <rdfs:subClassOf>, <vertebrates>)</code>. Therefore, the function generates the statement <code>(<marsupials>, <rdfs:subClassOf>, <vertebrates>)</code>.</p>
+
+<p>Using the query across the existing set of statements produces the following new set of statements:</p>
+
+<p class="commandtext">[ (<code><marsupials>, <rdfs:subClassOf>, <vertebrates></code>)<br />
+ (<kangaroos>, <rdfs:subClassOf>, <<code>vertebrates</code>>)<br />
+ (<red-kangaroos>, <rdfs:subClassOf>, <<code>vertebrates</code>>)<br />
+ (<placental-mammals>, <rdfs:subClassOf>, <<code>vertebrates></code>)<br />
+ (<elephants>, <rdfs:subClassOf>, <<code>vertebrates</code>>)<br />
+ (<kangaroos>, <rdfs:subClassOf>, <mammals>)<br />
+ (<red-kangaroos>, <rdfs:subClassOf>, <mammals>)<br />
+ (<elephants>, <rdfs:subClassOf>, <mammals>)<br />
+ (<red-kangaroos>, <rdfs:subClassOf>, <marsupials>) ]</p>
+
+<p>To provide the results expected from a transitive closure function you would union together these newly generated statements with the original base set of statements, using the following query:</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />
+...<br />
+where trans($subject <rdfs:subClassOf> $object)<br />
+or $subject <rdfs:subClassOf> $object;</p>
+
+<p>You can further restrict the <code>trans</code> function to a sub-set of statements, as shown in the following example.</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />
+...<br />
+where trans($subject <rdfs:subClassOf> <mammals><br />
+and $subject <rdfs:subClassOf> $object);</p>
+
+<p>This produces new statements where the object in the inheritance tree begins with <code><mammals></code>, eliminating the statements derived from <code><vertebrates></code>. It produces the following:</p>
+
+<p class="commandtext">[ (<kangaroos>, <rdfs:subClassOf>, <mammals>)<br />
+ (<red-kangaroos>, <rdfs:subClassOf>, <mammals>)<br />
+ (<elephants>, <rdfs:subClassOf>, <mammals>)<br />
+ (<red-kangroos>, <rdfs:subClassOf>, <marsupials>) ]</p>
+
+<p>To get the full transitive closure, the newly inferred statements are unioned with the base statements. To only return the sub-graph from <code><mammals></code> we can add the results from a <code><a id="h1537" class="documentlinktemplate" title="Traversing a Graph (walk Function)" href="187.htm#o1532">walk</a></code> function:</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />
+...<br />
+where trans($xxx <rdfs:subClassOf> <mammals><br />
+and $subject <rdfs:subClassOf> $object) or<br />
+walk($subject <rdfs:subClassOf> <mammals><br />
+and $subject <rdfs:subClassOf> $object);</p>
+
+<p>To generate the statements to <code><marsupials></code> you can constrain the subject in the function instead:</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />
+...<br />
+where trans(<marsupials> <rdfs:subClassOf> $object<br />
+and $subject <rdfs:subClassOf> $object) ;</p>
+
+<p>This produces:</p>
+
+<p class="commandtext">[ <marsupials>, <rdfs:subClassOf>, <vertebrates>) ]</p>
+
+<p>The <code>trans</code> function also allows you to limit what is inferred by dropping the second constraint within the <code>trans</code> definition. For example, to infer only direct statements from <code><vertebrates></code>:</p>
+
+<p class="commandtext">select $subject <rdfs:subClassOf> <<code>vertebrates</code>><br />
+...<br />
+where trans($subject <rdfs:subClassOf> <<code>vertebrates</code>>)</p>
+
+<p>Which produces:</p>
+
+<p class="commandtext">[ (<marsupials>, <rdfs:subClassOf>, <<code>vertebrates</code>>)<br />
+ (<kangaroos>, <rdfs:subClassOf>, <<code>vertebrates</code>>)<br />
+ (<red-kangaroos>, <rdfs:subClassOf>, <<code>vertebrates</code>>)<br />
+ (<placental-mammals>, <rdfs:subClassOf>, <<code>vertebrates</code>>)<br />
+ (<elephants>, <rdfs:subClassOf>, <<code>vertebrates</code>>) ]</p>
+
+<p>Likewise, you can also make the subject in the <code>trans</code> constraint a constant and the object a variable.</p>
+<a name="o2768"></a><h4>exclude Function</h4>
+
+<p>The <code>exclude</code> function allows you to select all statements whose properties are the inverse of a given constraint. Normal constraints match against the graph with the constraints you provide. Constraints enclosed in an <code>exclude</code> function return the values in the graph that are not the constraints provided. This allows you to build queries to ask questions such as: "find me all the known plants stored, with leaves that are not green" or "find me all the American states stored that are not Alabama".</p>
+
+<p>Using the following statements as an example:</p>
+
+<p class="commandtext">[ (<maple>, <leaves>, 'green')<br />
+ (<redMaple>, <leaves>, 'red')<br />
+ (<oak>, <leaves>, 'green')<br />
+ (<cactus>, <prickles>, 'yellow') ]</p>
+
+<p>You wish to find all plants that do not have leaves. The following query:</p>
+
+<p class="commandtext">select $s $p $o<br />
+...<br />
+where exclude($s <leaves> $o) <br />
+and ($s $p $o);</p>
+
+<p>Returns:</p>
+
+<p class="commandtext">[ (<cactus>, <prickles>, 'yellow') ]</p>
+
+<p>Unless your model is very small, the <code>exclude</code> function by itself is rarely useful. For example, the following query:</p>
+
+<p class="commandtext">select $s $p $o<br />
+...<br />
+where exclude($s <leaves> 'green')<br />
+and $s $p $o;</p>
+
+<p>Returns:</p>
+
+<p class="commandtext">[ (<cactus>, <prickles>, 'yellow')<br />
+ (<redMaple), <leaves>, 'red' ]</p>
+
+<p>As this returns all statements that do not have the predicate <code><leaves></code> and the object value 'green', if a statement exists where <em>either</em> of these columns do not match, it is returned. If you want to find all the things that have leaves that are not green you need to perform the following query:</p>
+
+<p class="commandtext">select $s<br />
+...<br />
+where $s <urn:leaves> $o <br />
+and exclude($s $p 'green');</p>
+
+<p>To understand what this query is doing, examine each constraint individually:</p>
+<ol class="listnumber"><li class="listnumber"><code>$s <urn:leaves> $o</code> returns all statements with the predicate <code><leaves></code>:
+<p class="listcontinuecommandtext">$s $o<br />
+<maple> 'green'<br />
+<redMaple> 'red'<br />
+<oak> 'green'</p>
+</li><li class="listnumber"><code>exclude($s $p 'green')</code> returns all statements that do not have the object value 'green':
+<p class="listcontinuecommandtext">$s $p<br />
+<redMaple> <leaves><br />
+<cactus> <prickles></p>
+</li></ol>
+<p>Combining these two results (using <code>and</code>), only one statement satisfies all constraints and the query returns the variable (<code>$s</code>) in the <code><a id="h217_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188">select</a></code> clause:</p>
+
+<p class="commandtext">[ (<redMaple>) ]</p>
+
+<p>Rarely do graphs contain just one easily defined set of statement. Extending the base set of statements with overlapping predicates for our example:</p>
+
+<p class="commandtext">[ (<maple>, <type>, <plant>)<br />
+ (<redMaple>, <type>, <plant>)<br />
+ (<oak>, <type>, <plant>)<br />
+ (<cactus>, <type>, <plant>)<br />
+ (<maple>, <leaves>, 'green')<br />
+ (<redMaple>, <leaves>, 'red')<br />
+ (<oak>, <leaves>, 'green')<br />
+ (<cactus>, <prickles>, 'yellow') <br />
+ (<binderRefill>, <leaves>, '50') ]</p>
+
+<p>Using the previous query:</p>
+
+<p class="commandtext">select $s<br />
+...<br />
+where $s <urn:leaves> $o <br />
+and exclude($s $p 'green');</p>
+
+<p>Returns:</p>
+
+<p class="commandtext">[ (<maple>)<br />
+ (<redMaple>)<br />
+ (<oak>)<br />
+ (<binderRefill>) ]</p>
+
+<p>Examining each constraint individually again:</p>
+<ol class="listnumber"><li class="listnumber"><code>$s <urn:leaves> $o</code> returns all statements with the predicate <code><leaves></code>:
+<p class="listcontinuecommandtext">$s $o<br />
+<maple> 'green'<br />
+<redMaple> 'red'<br />
+<oak> 'green'<br />
+<binderRefill> '50'</p>
+</li><li class="listnumber"><code>exclude($s $p 'green')</code> returns all statements that do not have the object value 'green':
+<p class="listcontinuecommandtext">$s $p<br />
+<maple> <type><br />
+<redMaple> <type><br />
+<oak> <type><br />
+<cactus> <type><br />
+<redMaple> <leaves><br />
+<cactus> <prickles><br />
+<binderRefill> <leaves></p>
+</li></ol>
+<p>Combining the <code>$s</code> column from each result of the constraints, leads to the result.</p>
+
+<p>You usually need to restrict the <code>exclude</code> constraint. In the previous examples, you only want to query things that are plants and not the entire graph. It is also preferable that the results from these constraints exist as real statements in a graph. To restrict the constraints so they only return things in the graph, the variables must be bound to the relevant positions.</p>
+
+<p>For example, the following query:</p>
+
+<p class="commandtext"><code>select $s $p $o<br />
+...<br />
+where $s <urn:leaves> $o <br />
+and exclude($s $p 'green') <br />
+and $s $p $o;</code></p>
+
+<p>Returns:</p>
+
+<p class="commandtext"><code>[ (<redMaple>, <leaves>, 'red')<br />
+ (<binderRefill>, <leaves>, '50') ]</code></p>
+
+<p>Note that the query still has not restricted the type of the object. To only query plants, the following query:</p>
+
+<p class="commandtext"><code>select $s $p $o<br />
+...<br />
+where $s <urn:leaves> $o <br />
+and exclude($s $p 'green') <br />
+and $s $p $o<br />
+and $s <type> <plant> ;</code></p>
+
+<p>Returns:</p>
+
+<p class="commandtext"><code>[ (<redMaple>, <leaves>, 'red') ]</code></p>
+<a name="o2769"></a><h5>Standard Queries</h5>
+
+<p>The variable names used in the <code>exclude</code> function are not bound by other constraints, including the <code><code><a id="h2772" class="documentlinktemplate" title="Assigning a Value to a Variable (mulgara:is)" href="187.htm#o1531"><mulgara:is></a></code></code> operation. All other operations match statements in the graph. So it is not the same thing as replacing positively matching values from the graph and assigning these values to the <code>exclude</code> function. The variable names used in the <code>exclude</code> function and other operations are only used to join the column values from the results of each constraint.</p>
+
+<p>For example, the query:</p>
+
+<p class="commandtext"><code>select $s $p $o<br />
+...<br />
+where exclude($s $p 'green')<br />
+and $p <mulgara:is> <leaves><br />
+and $s $p $o;</code></p>
+
+<p>Results in all the statements that do not have the object value 'green', combined with all the statements with the predicate <code><leaves></code>:</p>
+
+<p class="commandtext"><code>[ (<redMaple>, <leaves>, 'red')<br />
+ (<binderRefill>, <leaves>, '50') ]</code></p>
+
+<p>Note that this is not the same as:</p>
+
+<p class="commandtext"><code>select $s $p $o<br />
+...<br />
+where exclude ($s <urn:leaves> 'green')<br />
+and $p <mulgara:is> <leaves><br />
+and $s $p $o;</code></p>
+
+<p>Which returns:</p>
+
+<p class="commandtext"><code>[ (<maple>, <leaves>, 'green')<br />
+ (<oak>, <leaves>, 'green') ]</code></p>
+<a name="o2770"></a><h5>exclude($s $p $o)</h5>
+
+<p><code>exclude</code> functions that only contain variables usually return no result. If joined to other constraints with <code>and</code>, it will return no result. As stated above, this cannot be changed by using <code><a id="h2772_2" class="documentlinktemplate" title="Assigning a Value to a Variable (mulgara:is)" href="187.htm#o1531"><mulgara:is></a></code> or other constraints. The only exception to this is when the <code>exclude</code> function is used in a subquery or aggregate function. See the next section on subqueries for more details.</p>
+
+<p>For example, the following query returns no result.</p>
+
+<p class="commandtext"><code>select $s $p $o<br />
+...<br />
+where exclude ($s $p $o)<br />
+and $o <mulgara:is> 'green'<br />
+and $s $p $o;</code></p>
+<a name="o2771"></a><h5>Subqueries</h5>
+
+<p>Subqueries allow the results from one query to be used in another. That is, the values of the outer queries bind to the variables with the same name in the inner query. So a constraint such as <code>exclude($s $p $o)</code>, which normally returns no result, could return results if used in a <code><code><a id="h211" class="documentlinktemplate" title="subquery Function" href="187.htm#o193">subquery</a></code></code> or <code><a id="h733" class="documentlinktemplate" title="count Function" href="187.htm#o194">count</a></code> function when any of the variables <code>$s</code>, <code>$p</code> or <code>$o</code> are bound by the outer query.</p>
+
+<p>For example, the following query binds the <code>$s</code> and <code>$o</code> values of the internal query:</p>
+
+<p class="commandtext"><code>select $s $o subquery(<br />
+ select $s2 $p2 $o2 <br />
+ ...<br />
+ where exclude($s $p2 $o) <br />
+ and $s $p2 $o2 <br />
+ and $s2 $p2 $o)<br />
+...<br />
+where $s <urn:type> $o ;</code></p>
+
+<p>The first result passes values to the internal <code>subquery</code> where <code>$s</code> is <code><maple></code> and <code>$o</code> is <code><plant></code>. This causes the inner query to look like:</p>
+
+<p class="commandtext"><code>select $s2 $p2 $o2 <br />
+...<br />
+where exclude(<maple> $p2 <plant>)<br />
+and <maple> $p2 $o2 <br />
+and $s2 $p2 <plant></code></p>
+<a name="o190"></a><h3>order by Clause</h3>
+
+<p>Optionally sorts the results of a <code><a id="h207_2" class="documentlinktemplate" title="select" href="187.htm">select</a></code> command according to the variables specified.</p>
+
+<p>The following example sorts the results numerically by rating (assuming ratings can be parsed as numbers), then alphabetically by author for documents of equal rating.</p>
+
+<p class="commandtext">... order by $rating $title;</p>
+
+<p>The suffixes <code>asc</code> and <code>desc</code> may be used to override the default sort ordering for a variable.</p>
+
+<p>The following example sorts the results such that low ratings display first, and then alphabetically by author for documents of equal rating.</p>
+
+<p class="commandtext">... order by $rating asc $author;</p>
+<a name="o191"></a><h3>limit Clause</h3>
+
+<p>Optionally limits the query result to a specified non-negative number of rows.</p>
+
+<p>When using <code>limit</code>, it is advisable to use the <code><a id="h219_2" class="documentlinktemplate" title="order by Clause" href="187.htm#o190">order by</a></code> clause to constrain the result rows into a unique order. Otherwise you do not know which rows are returned. For example, if you limit a result to 10 rows without specifying an order, you do not know which 10 rows are returned.</p>
+<a name="o192"></a><h3>offset Clause</h3>
+
+<p>Optionally skips a non-negative number of rows at the beginning of a query result. The use of <code>offset</code> usually accompanies a <code><a id="h221_2" class="documentlinktemplate" title="limit Clause" href="187.htm#o191">limit</a></code> clause, making it possible to page through results.</p>
+
+<p>As with <code>limit</code>, it is advisable to use the <code><a id="h219_3" class="documentlinktemplate" title="order by Clause" href="187.htm#o190">order by</a></code> clause to constrain the result rows into a unique order.</p>
+
+<p>For examples and explanations of complete queries, see the <a id="h666" class="documentlinktemplate" title="Basic iTQL Operations" href="230.htm">Issuing iTQL Commands section</a>.</p>
+<a name="o193"></a><h3>subquery Function</h3>
+
+<p>Used to nest <code><a id="h207_3" class="documentlinktemplate" title="select" href="187.htm">select</a></code> commands. Subqueries nest inside <code>select</code> by binding variables in the subquery <code><a id="h1321_2" class="documentlinktemplate" title="where Clause" href="187.htm#o197">where</a></code> clause to the outer <code><a id="h1298_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188">select</a></code> clause.</p>
+
+<p>In the following example the value of <code>$vcard</code> is bound to the inner query. The outer result set contains nested result sets for each subquery.</p>
+
+<p class="commandtext">select $vcard $fn <br />
+ subquery( select $title <br />
+ from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title<br />
+ order by $title )<br />
+ from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br />
+ order by $fn;</p>
+
+<p>The above example produces the following XML output from a SOAP call:</p>
+
+<p class="commandtext"><?xml version="1.0"?><br />
+<answer xmlns="http://mulgara.org/tql#"><br />
+ <query><br />
+ <variables><br />
+ <vcard/><br />
+ <fn/><br />
+ <k0/><br />
+ </variables><br />
+ <solution><br />
+ <vcard resource="http://qqq.com/staff/superman"/><br />
+ <fn>Superman</fn><br />
+ <k0><br />
+ <variables><br />
+ <title/><br />
+ </variables><br />
+ </k0><br />
+ </solution><br />
+ <solution><br />
+ <vcard resource="http://qqq.com/staff/spiderman"/><br />
+ <fn>Peter Parker</fn><br />
+ <k0><br />
+ <variables><br />
+ <title/><br />
+ </variables><br />
+ <solution><br />
+ <title>Super Hero</title><br />
+ </solution><br />
+ <solution><br />
+ <title>PO2</title><br />
+ </solution><br />
+ </k0><br />
+ </solution><br />
+ <solution><br />
+ <vcard resource="http://qqq.com/staff/corky"/><br />
+ <fn>Corky Crystal</fn><br />
+ <k0><br />
+ <variables><br />
+ <title/><br />
+ </variables><br />
+ <solution><br />
+ <title>Computer Officer Class 3</title><br />
+ </solution><br />
+ </k0><br />
+ </solution><br />
+ </query><br />
+</answer></p>
+<a name="o194"></a><h3>count Function</h3>
+
+<p>Similar to <code><a id="h211_2" class="documentlinktemplate" title="subquery Function" href="187.htm#o193">subquery</a></code> except that it only returns a dummy variable with value of the total row count of the inner query. See the <code><a id="h1320" class="documentlinktemplate" title="select Clause" href="187.htm#o188">select</a></code><a id="h1320_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188"> clause section</a> for a description of dummy variables. For example:</p>
+
+<p class="commandtext">select $vcard $fn <br />
+ count( select $title from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br />
+ from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn ;</p>
+
+<p>The above example returns the following:</p>
+
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"<br />
+vcard=http://qqq.com/staff/spiderman fn="Peter Parker" k0="2"<br />
+vcard=http://qqq.com/staff/superman fn="Superman" k0="0"</p>
+<a name="o2776"></a><h3>having Clause</h3>
+
+<p>The <code>having</code> clause applies a constraint to a dummy variable that results from a <code><a id="h1323" class="documentlinktemplate" title="subquery Function" href="187.htm#o193">subquery</a></code> in a <code><a id="h1320_3" class="documentlinktemplate" title="select Clause" href="187.htm#o188">select</a></code><a id="h1320_4" class="documentlinktemplate" title="select Clause" href="187.htm#o188"> clause</a> of a query. These variables are of the form <code>$k0</code>, <code>$k1</code>, <code>$k2</code>, … <code>$kn</code> and only hold numerical values. See the <code><a id="h1320_5" class="documentlinktemplate" title="select Clause" href="187.htm#o188">select</a></code><a id="h1320_6" class="documentlinktemplate" title="select Clause" href="187.htm#o188"> clause section</a> for a description of dummy variables.</p>
+
+<p>There are four special predicates that can be used to perform arithmetic comparisons in the <code>having</code> clause, as outlined in the following table.</p>
+<table width="450" cellpadding="2" cellspacing="0" border="0" style="border-collapse:collapse">
+<tr align="left" valign="top">
+<td width="294">
+<p class="tableheading">Predicate</p>
+</td>
+<td width="156">
+<p class="tableheading">Arithmetic Operation</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294">
+<p class="tablebodytext"><code>http://mulgara.org/mulgara#occurs</code></p>
+</td>
+<td width="156">
+<p class="tablebodytext">=</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294">
+<p class="tablebodytext"><code>http://mulgara.org/mulgara#occursMoreThan</code></p>
+</td>
+<td width="156">
+<p class="tablebodytext">></p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294">
+<p class="tablebodytext"><code>http://mulgara.org/mulgara#occursLessThan</code></p>
+</td>
+<td width="156">
+<p class="tablebodytext"><</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294">
+<p class="tablebodytext"><code>http://mulgara.org/mulgara#notOccurs</code></p>
+</td>
+<td width="156">
+<p class="tablebodytext">?</p>
+</td>
+</tr>
+
+</table>
+
+<p>Expanding on the example shown in the <code><a id="h1323_2" class="documentlinktemplate" title="subquery Function" href="187.htm#o193">subquery</a></code> and <code><a id="h733_2" class="documentlinktemplate" title="count Function" href="187.htm#o194">count</a></code> sections, the following query restricts the result to those with a count of 1:</p>
+
+<p class="commandtext">select $vcard $fn <br />
+ count( select $title from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br />
+ from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br />
+ having $k0 <http://mulgara.org/mulgara#occurs><br />
+ '1.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+
+<p>The above example returns:</p>
+
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"</p>
+
+<p>Similarly, to restrict the result to those with a count greater than 0 would be: </p>
+
+<p class="commandtext">select $vcard $fn <br />
+ count( select $title from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br />
+ from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br />
+ having $k0 <http://mulgara.org/mulgara#occursMoreThan><br />
+ '0.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+
+<p>The above example returns:</p>
+
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"<br />
+vcard=http://qqq.com/staff/spiderman fn="Peter Parker" k0="2"</p>
+
+<p>The form of the constraint for the <code>having</code> clause must be:</p>
+
+<p class="commandtext">$kx predicate value^^<http://www.w3.org/2001/XMLSchema#double></p>
+
+<p>Where p<code>redicate</code> is one of the predicates from the above table.</p>
+
+<p>Note that compound constraints for the <code>having</code> clause are not allowed. For example, the following query is <em>not</em> legal:</p>
+
+<p class="commandtext">select $vcard $fn <br />
+ count( select $title from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br />
+ from <rmi://mysite.com/server1#vcard> <br />
+ where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br />
+ having $k0 <http://mulgara.org/mulgara#occurs><br />
+ '0.0'^^<http://www.w3.org/2001/XMLSchema#double> <br />
+ or $k0 <http://mulgara.org/mulgara#occurs> <br />
+ '2.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+
+
+ </td>
+ <td width=20>
+ </td>
+ <td align="left">
+ <a href="http://www.opensource.org/docs/definition.php" title="Open Source Initiative" target="_blank"><img style="border:0;width:110px;height:95;" src="http://www.opensource.org/trademarks/opensource/web/opensource-110x95.png" alt="Open Source logo" /></a>
+
+
+</td>
+</tr>
+<tr valign="bottom">
+<td>
+<br>
+
+
+<p class="toc">© 2001-2004 Tucana Technologies, Inc. Some rights reserved.</p>
+<p class="toc">© 2006 The Mulgara Project. Some rights reserved.<br>
+Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "<a href="fdl.txt">GNU Free Documentation License</a>".</p>
+</td>
+</tr>
+</table>
+
+</html>
+
+
Added: trunk/docs/oldSite/187.htm.r139
===================================================================
--- trunk/docs/oldSite/187.htm.r139 2006-12-08 00:07:07 UTC (rev 146)
+++ trunk/docs/oldSite/187.htm.r139 2006-12-08 00:08:59 UTC (rev 147)
@@ -0,0 +1,307 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
+"http://www.w3.org/TR/html4/loose.dtd">
+<html>
+<head>
+<title> select </title>
+<link rel="icon" type="text/png"
+href="./media/images/icons/siteicon.png" />
+<link rel="shortcut icon" type="text/png" href="siteicon.png" />
+
+<meta name="author" content="Tom Adams" />
+<meta name="copyright" content="Copyright © 2003, Kowari Project" />
+<meta name="robots" content="all" />
+<meta name="description" content="Mulgara Project Home" />
+<meta name="keywords" content="select mulgara, mulgara project, metadata, metastore, metadatabase, datastore, database, scaleable, scalable, transaction, java, open source, mulgara, homepage" />
+<meta name="location" content="Global" />
+<meta name="document-distribution" content="Global" />
+
+<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
+<meta http-equiv="dialect" content="AU" />
+<meta http-equiv="language" content="English" />
+<meta http-equiv="window-target" content="_top" />
+
+<meta name="DC.Title" content="Mulgara : metastore" />
+<meta name="DC.Creator" content="Tom Adams" />
+<meta name="DC.Creator.Address" content="http://www.adams.id.au/tom/index.php" />
+<!--<meta name="DC.Contributor" content="Andrew Newman" />-->
+<meta name="DC.Subject" content="Mulgara Project Home" />
+<meta name="DC.Description" content="Mulgara Project Home" />
+<meta name="DC.Date.Created" scheme="iso8601" content="2003-09-22" />
+<meta name="DC.Modified" scheme="iso8601" content="2003-09-22" />
+<meta name="DC.Language" scheme="rfc1766" content="en" />
+<meta name="DC.Rights" scheme="URI" content="http://mulgara.org/docs/legal.html" />
+<meta name="DC.Type" content="Text.Homepage.Personal" />
+<meta name="DC.Identifier" scheme="URI" content="http://mulgara.org/index.php" />
+
+<meta name="Generator" content="AITPublish" />
+
+<link rel="stylesheet" href="mulgara_stylesheet.css">
+<!-- <link rel="stylesheet" href="44.css"> -->
+<base target="BODY">
+</head>
+<body>
+<table border="0" width="100%">
+<tr valign="top">
+<td width="80%">
+<table cellpadding="0" cellspacing="0" border="0">
+<tr valign="top">
+<td width= "18">
+<p class="prevnextbutton"><a href="186.htm" target="_self"><img src="previous.gif" alt="Previous Topic" height="25px" width="23px" vspace="2" hspace="2" align="bottom" border="0" /></a></p></td>
+<td width= "18">
+<p class="prevnextbutton"><a href="195.htm" target="_self"><img src="next.gif" alt="Next Topic" height="25px" width="23px" vspace="2" hspace="2" align="bottom" border="0" /></a></p></td>
+</tr>
+</table>
+<h2 class="heading2">select</h2>
+<p class="bodytext">Issues queries to Mulgara<sup class="superscript">TM</sup> servers and displays the corresponding results. The command consists of a sequence of <code class="monospace"><a id="h217" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code>, <code class="monospace"><a id="h218" class="documentlinktemplate" title="from Clause" href="187.htm#o189" target="_self">from</a></code>, and <code class="monospace"><a id="h206" class="documentlinktemplate" title="where Clause" href="187.htm#o197" target="_self">where</a></code> clauses; and may optionally include <code class="monospace"><a id="h219" class="documentlinktemplate" title="order by Clause" href="187.htm#o190" target="_self">order by</a></code>, <code class="monospace"><a id="h220" class="documentlinktemplate" title="offset Clause" href="187.htm#o192" target="_self">offset</a></code> and <code class="monospace"><a id="h221" class="documentlinktemplate" title="limit Clause" href="187.htm#o191" target="_self">limit</a></code> clauses. With all clauses present, the general syntax is as follows:</p>
+<p class="commandtext">select columns from models where constraints order by variables limit count offset count;</p>
+<p class="bodytext">The purpose of the <code class="monospace">select</code> command is to find values for some set of variables that satisfy the specified constraints. All variable names start with a dollar sign (<code class="monospace">$)</code>, for example <code class="monospace">$x</code> or <code class="monospace">$title</code>.</p>
+<table cellpadding="0" cellspacing="0" border="0">
+<tr valign="top">
+<td width= "226.8">
+<p class="relatedheading">In This Section</p><p class="relateditem"><a href="187.htm#o188" target="_self">select Clause</a></p><p class="relateditem"><a href="187.htm#o189" target="_self">from Clause</a></p><p class="relateditem"><a href="187.htm#o197" target="_self">where Clause</a></p><p class="relateditem"><a href="187.htm#o190" target="_self">order by Clause</a></p><p class="relateditem"><a href="187.htm#o191" target="_self">limit Clause</a></p><p class="relateditem"><a href="187.htm#o192" target="_self">offset Clause</a></p><p class="relateditem"><a href="187.htm#o193" target="_self">subquery Function</a></p><p class="relateditem"><a href="187.htm#o194" target="_self">count Function</a></p><p class="relateditem"><a href="187.htm#o2776" target="_self">having Clause</a></p></td>
+<td width= "226.8">
+<p class="relatedheading">See Also</p><p class="relateditem"><a href="271.htm" target="_self">iTQL Commands</a></p><p class="relateditem"><a href="170.htm" target="_self">alias</a></p><p class="relateditem"><a href="171.htm" target="_self">backup</a></p><p class="relateditem"><a href="223.htm" target="_self">comment (#)</a></p><p class="relateditem"><a href="174.htm" target="_self">commit</a></p><p class="relateditem"><a href="176.htm" target="_self">create</a></p><p class="relateditem"><a href="178.htm" target="_self">delete</a></p><p class="relateditem"><a href="179.htm" target="_self">drop</a></p><p class="relateditem"><a href="180.htm" target="_self">execute</a></p><p class="relateditem"><a href="181.htm" target="_self">help</a></p><p class="relateditem"><a href="182.htm" target="_self">insert</a></p><p class="relateditem"><a href="183.htm" target="_self">load</a></p><p class="relateditem"><a href="184.htm" target="_self">quit</a></p><p class="relateditem"><a href="185.htm" target="_self">restore</a></p><p class="relateditem"><a href="186.htm" target="_self">rollback</a></p><p class="relateditem"><a href="195.htm" target="_self">set</a></p></td>
+</tr>
+</table>
+
+<a name="o188"></a><h3 class="heading3">select Clause</h3>
+<p class="bodytext">Specifies the variables to solve for and their order in the result. For example:</p>
+<p class="commandtext">select $title $author $date ...</p>
+<p class="bodytext">Constant resource or literal values may be part of a <code class="monospace">select</code> clause. In these cases, dummy variable names (<code class="monospace">$k0</code>, <code class="monospace">$k1</code>, <code class="monospace">$k2</code>, … <code class="monospace">$kn</code>) are created for the constant values.</p>
+<p class="bodytext">The following example returns three columns: <code class="monospace">$k0</code>, <code class="monospace">$x</code> and <code class="monospace">$k1</code> where the values of <code class="monospace">$k0</code> and <code class="monospace">$k1</code> for every solution are the literal value <code class="monospace">foo</code> and the resource value <code class="monospace">http://www.site.domain.net</code> respectively.</p>
+<p class="commandtext">select 'foo' $x <http://www.site.domain.net> ...</p>
+<a name="o189"></a><h3 class="heading3">from Clause</h3>
+<p class="bodytext">Specifies the model to query. For example:</p>
+<p class="commandtext">... from <rmi://mysite.com/server1#model1> ...</p>
+<p class="bodytext">Because models are sets of statements, it is logical to compose them using set operations. The <code class="monospace">from </code>clause permits set union using the <code class="monospace">or</code> operator and set intersection using the <code class="monospace">and</code> operator, with parentheses used to control association.</p>
+<a name="o3149"></a>
+<p class="bodytext">The following example queries only the statements appearing in all three models. </p>
+<p class="commandtext">... from <rmi://mysite.com/server1#model1> and <rmi://mysite.com/server1#model2><br /> and <rmi://mysite.com/server1#model3> ...</p>
+<a name="o197"></a><h3 class="heading3">where Clause</h3>
+<p class="bodytext">The <code class="monospace">where</code> clause is usually the largest and most detailed clause of the <code class="monospace"><a id="h207" class="documentlinktemplate" title="select" href="187.htm" target="_self">select</a></code> command. It specifies the constraints that must be satisfied by the variable values in each solution. A constraint is a sequence of subject, predicate and object that represents an RDF statement. Each of the three positions is either a constant value (a resource or a literal) or a variable. The Mulgara server finds values for any variables such that the resulting statement is present in the model that was specified in the preceding <code class="monospace"><a id="h1326" class="documentlinktemplate" title="from Clause" href="187.htm#o189" target="_self">from</a></code> clause.</p>
+<p class="bodytext">For example, the following <code class="monospace">where</code> clause constrains that in all solutions, the value of <code class="monospace">$title</code> is the title of the resource referred to in <code class="monospace">$document</code>.</p>
+<p class="commandtext">... where $document <dc:title> $title ...</p>
+<p class="bodytext">Constraints may be composed using <code class="monospace">and</code> and <code class="monospace">or</code> operations, with parentheses to control association.</p>
+<p class="bodytext">The following example returns every document with a title, an author and a subject of either botany or zoology. Documents without a known title or author are not returned.</p>
+<p class="commandtext">... where $document <dc:title> $title and $document <dc:creator> $author <br /> and ($document <dc:subject> 'botany' or $document <dc:subject> 'zoology') ...</p>
+<a name="o1530"></a><h4 class="heading4">in Specifier</h4>
+<p class="bodytext">Constraints may optionally contain an <code class="monospace">in</code> specifier to resolve the constraint against the statements in a specified model, rather than the one specified in the <code class="monospace"><a id="h1303" class="documentlinktemplate" title="from Clause" href="187.htm#o189" target="_self">from</a></code> clause.</p>
+<p class="bodytext">The <code class="monospace">in</code> specifier may be used to specify views as well as models.</p>
+
+<p class="bodytext">The following example constrains the result by titles in the <code class="monospace">#books</code> model rather than the one specified in the <code class="monospace">from</code> clause.</p>
+<p class="commandtext">... where $document <dc:title> $title in <rmi://mysite.com/server1#books> ...</p>
+<a name="o1531"></a><h4 class="heading4">Assigning a Value to a Variable (tucana:is)</h4>
+<p class="bodytext">Constraints may also assign a value to a variable rather then querying for it. The special property <code class="monospace">http://tucana.org/tucana#is </code>(or the aliased form <code class="monospace"><tucana:is></code>) can be used with a variable as its subject and a non-variable value as its object. This assigns the non-variable value to the variable.</p>
+<p class="bodytext">The following example results in every document authored by Mendel about genetics, or by Mendeleev about chemistry.</p>
+<p class="commandtext">... where $document <dc:title> $title and $document <dc:creator> $author <br /> and $document <dc:subject> $subject <br /> and (($author <tucana:is> 'Mendel' and $subject <tucana:is> 'genetics' ) <br /> or ($author <tucana:is> 'Mendeleev' and $subject <tucana:is> 'chemistry')) ...</p>
+<a name="o1532"></a><h4 class="heading4">Traversing a Graph (walk Function)</h4>
+<p class="bodytext">Traversing a graph allows a query to return values, based on a predicate, by following up or down a hierarchy of statements. In a schema language such as RDFS, these hierarchies are expressed as a sub-class or sub-property predicate. Traversing a graph is performed with the <code class="monospace">walk</code> function within a <code class="monospace"><a id="h1321" class="documentlinktemplate" title="where Clause" href="187.htm#o197" target="_self">where</a></code> clause.</p>
+<p class="bodytext">The syntax of the <code class="monospace">walk</code> function is either:</p>
+<p class="listcontinuecommandtext">walk ($subject_variable <predicate_URI> <object_URI> and<br />$subject_variable <predicate_URI> $object_variable)</p>
+<p class="listcontinue">or</p>
+<p class="listcontinuecommandtext">walk (<subject_URI> <predicate_URI> $object_variable and<br />$subject_variable <predicate_URI> $object_variable)</p>
+<p class="bodytext">The <code class="monospace">walk</code> function must be bound to a <code class="monospace"><a id="h1298" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code> clause using the same triple pattern that matches the second parameter. For example:</p>
+<p class="commandtext">select $subject <predicate_URI> $object<br />...<br />where walk ($subject <predicate_URI> <object_URI> and<br />$subject <predicate_URI> $object);</p>
+<p class="bodytext">An example of <code class="monospace">walk</code> is demonstrated using the following statements:</p>
+<p class="commandtext">[ ( <kangroos>, <rdfs:subClassOf>, <marsupials> )<br /> ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br /> ( <placental-mammals>, <rdfs:subClassOf>, <mammals> )<br /> ( <mammals>, <rdfs:subClassOf>, <vertebrates> ) ]</p>
+<p class="bodytext">To query a set of statements in the hierarchy ending with <code class="monospace"><vertebrates></code> as an object:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where walk($subject <rdfs:subClassOf> <vertebrates><br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">Working from the bottom up, the system:</p>
+<ul class="listbullet"><li class="listbullet">Matches <code class="monospace">( <mammals>, <rdfs:subClassOf>, <vertebrates> )</code> and then substitutes <code class="monospace"><mammals></code> for <code class="monospace"><vertebrates></code> in the constraints.</li><li class="listbullet">Attempts to match for the triples <code class="monospace">( *, <rdfs:subClassOf>, <mammals> )</code>.</li><li class="listbullet">Then matches for <code class="monospace">( <marsupials>, <rdfs:subClassOf>, <mammals> )</code> and <code class="monospace">( <placental-mammals>, <rdfs:subClassOf>, <mammals> )</code>.</li><li class="listbullet">Then matches for <code class="monospace">( *, <rdfs:subClassOf>, <marsupials> )</code> and (<code class="monospace"> *, <rdfs:subClassOf>, <placental-mammals> )</code> and so on.</li></ul><p class="bodytext">The result of the query is:</p>
+<p class="commandtext">[ ( <mammals>, <rdfs:subClassOf>, <vertebrates> )<br /> ( <placental-mammals>, <rdfs:subClassOf>, <mammals> )<br /> ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br /> ( <kangaroos>, <rdfs:subClassOf>, <marsupials> ) ]</p>
+<p class="bodytext">You can also traverse down the graph following the hierarchy. For example:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where walk(<kangaroos> <rdfs:subClassOf> $object<br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">This returns:</p>
+<p class="commandtext">[ ( <kangaroos>, <rdfs:subClassOf>, <marsupials> )<br /> ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br /> ( <mammals>, <rdfs:subClassOf>, <vertebrates> ) ]</p>
+<a name="o1535"></a><h4 class="heading4">Transitive Closure (trans Function)</h4>
+<p class="bodytext">Transitive closure provides the ability to express a function that generates new statements. Normally, transitive closure produces both existing and new statements. The <code class="monospace">trans</code> function in iTQL<sup class="superscript">TM</sup> only produces new statements, statements that did not exist in the model before it was executed. The <code class="monospace">trans</code> function can be further constrained by limiting which statements are inferred and by giving it a starting or termination point.</p>
+<p class="bodytext">The simplest form of the <code class="monospace">trans</code> function defines a predicate to operate on:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">This generates a new statement, <code class="monospace">$x <rdfs:subClassOf> $z</code>, when it finds two statements that match the pattern <code class="monospace">$x <rdfs:subClassOf> $y</code> and <code class="monospace">$y <rdfs:subClassOf> $z</code>.</p>
+<p class="bodytext">For example, consider the following set of statements:</p>
+<p class="commandtext">[ (<mammals>, <rdfs:subClassOf>, <vertebrates>)<br /> (<eats-leaves>, <rdfs:subPropertyOf>, <herbivore>)<br /> (<marsupials>, <rdfs:subClassOf>, <mammals>)<br /> (<placental-mammals>, <rdfs:subClassOf>, <mammals>)<br /> (<elephants>, <rdfs:subClassOf>, <placental-mammals>)<br /> (<kangaroos>, <rdfs:subClassOf>, <marsupials>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <kangaroos>) ]</p>
+<p class="bodytext">As a tree it looks as follows:</p>
+<p class="bodytext"><img src="1536.gif" alt="Transitive Closure" height="273" width="252" vspace="0" hspace="0" align="bottom" border="0" /></p>
+<p class="bodytext">Based on the constraint in the query, the first and third statements match the pattern <code class="monospace">(<marsupials>, <rdfs:subClassOf>, <mammals>) and (<mammals>, <rdfs:subClassOf>, <vertebrates>)</code>. Therefore, the function generates the statement <code class="monospace">(<marsupials>, <rdfs:subClassOf>, <vertebrates>)</code>.</p>
+<p class="bodytext">Using the query across the existing set of statements produces the following new set of statements:</p>
+<p class="commandtext">[ (<code class="monospace"><marsupials>, <rdfs:subClassOf>, <vertebrates></code>)<br /> (<kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<placental-mammals>, <rdfs:subClassOf>, <<code class="monospace">vertebrates></code>)<br /> (<elephants>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<elephants>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <marsupials>) ]</p>
+<p class="bodytext">To provide the results expected from a transitive closure function you would union together these newly generated statements with the original base set of statements, using the following query:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($subject <rdfs:subClassOf> $object)<br />or $subject <rdfs:subClassOf> $object;</p>
+<p class="bodytext">You can further restrict the <code class="monospace">trans</code> function to a sub-set of statements, as shown in the following example.</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($subject <rdfs:subClassOf> <mammals><br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">This produces new statements where the object in the inheritance tree begins with <code class="monospace"><mammals></code>, eliminating the statements derived from <code class="monospace"><vertebrates></code>. It produces the following:</p>
+<p class="commandtext">[ (<kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<elephants>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangroos>, <rdfs:subClassOf>, <marsupials>) ]</p>
+<p class="bodytext">To get the full transitive closure, the newly inferred statements are unioned with the base statements. To only return the sub-graph from <code class="monospace"><mammals></code> we can add the results from a <code class="monospace"><a id="h1537" class="documentlinktemplate" title="Traversing a Graph (walk Function)" href="187.htm#o1532" target="_self">walk</a></code> function:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($xxx <rdfs:subClassOf> <mammals><br />and $subject <rdfs:subClassOf> $object) or<br />walk($subject <rdfs:subClassOf> <mammals><br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">To generate the statements to <code class="monospace"><marsupials></code> you can constrain the subject in the function instead:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans(<marsupials> <rdfs:subClassOf> $object<br />and $subject <rdfs:subClassOf> $object) ;</p>
+<p class="bodytext">This produces:</p>
+<p class="commandtext">[ <marsupials>, <rdfs:subClassOf>, <vertebrates>) ]</p>
+<p class="bodytext">The <code class="monospace">trans</code> function also allows you to limit what is inferred by dropping the second constraint within the <code class="monospace">trans</code> definition. For example, to infer only direct statements from <code class="monospace"><vertebrates></code>:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> <<code class="monospace">vertebrates</code>><br />...<br />where trans($subject <rdfs:subClassOf> <<code class="monospace">vertebrates</code>>)</p>
+<p class="bodytext">Which produces:</p>
+<p class="commandtext">[ (<marsupials>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<placental-mammals>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<elephants>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>) ]</p>
+<p class="bodytext">Likewise, you can also make the subject in the <code class="monospace">trans</code> constraint a constant and the object a variable.</p>
+
+<a name="oxxminusxx"></a><h4 class="heading4">Graph Difference (minus) Function</h4>
+<p class="bodytext">The <code class="monospace">minus</code> function allows
+you to find the statements which differ between two graphs.</p>
+
+<p class="bodytext">For example, to find the statements which are different
+between the model <rmi://localhost/server1#input> and
+<rmi://localhost/server1#output>, we could issue a query like this:</p>
+
+<p class="commandtext">
+select $subject $predicate $object
+from <rmi://localhost/server1#output>
+where
+ $subject $predicate $object in <rmi://localhost/server1#output>
+ minus
+ $subject $predicate $object in <rmi://localhost/server1#input> ;
+</p>
+
+<p class="bodytext">The use of the <code class="monospace">in</code> specifier
+is not strictly necessary for the model named in <code
+class="monospace">from</code> clause, but it makes the query a bit more
+readable by providing symmetry.</p>
+
+<p class="bodytext">To count the number of statements that differ between the
+two models, we could do something like the following. Note variables do not
+carry over into a <code class="monospace">count</code> function’s
+namespace, so the outer query could be anything.</p>
+
+<p class="commandtext">
+select count (
+ select $subject $predicate $object
+ from <rmi://localhost/server1#output>
+ where
+ $subject $predicate $object in <rmi://localhost/server1#output>
+ minus
+ $subject $predicate $object in <rmi://localhost/server1#input>
+)
+from <rmi://localhost/server1#>
+where
+ $s $p $o ;
+</p>
+
+
+<a name="o2768"></a><h4 class="heading4">exclude Function</h4>
+<p class="bodytext">The <code class="monospace">exclude</code> function allows you to select all statements which do not match a given constraint. Normal constraints match against the graph with the constraints you provide. Constraints enclosed in an <code class="monospace">exclude</code> function return the values in the graph that are not the constraints provided.</p>
+<p class="bodytext">This function is almost never useful. Consider using the <a href="#oxxminusxx">minus</a> operator instead.</p>
+<p class="bodytext">Using the following statements as an example for "finding all plants with leaves that are not green":</p>
+<p class="commandtext">[ (<maple>, <leaves>, 'green')<br /> (<redMaple>, <leaves>, 'red')<br /> (<oak>, <leaves>, 'green')<br /> (<cactus>, <prickles>, 'yellow') ]</p>
+<p class="bodytext">With a small model it is possible to query for all plants that do not have leaves. The following query:</p>
+<p class="commandtext">select $s<br />from ...<br />where exclude($s <leaves> $o) ;</p>
+<p class="bodytext">Returns:</p>
+<p class="commandtext">[ ( <cactus> ) ]</p>
+<p class="bodytext">However, more statements in the data mean that the results will need to be constrained more carefully. Unfortunately this may cause the <code class="monospace">exclude</code> operator to miss some required statements. For instance, if the following statements were also included:</p>
+<p class="commandtext">[ ( <maple> <rdf:type> <plant> )<br/> ( <redMaple> <rdf:type> <plant> )<br/> ( <oak> <rdf:type> <plant> )<br/> ( <cactus> <rdf:type> <plant> ) ]</p>
+<p class="bodytext">The following query would appear appropriate:</p>
+<p class="commandtext">select $s<br />from ...<br />where $s <rdf:type> <plant> <br/>and exclude($s <leaves> $o);</p>
+<p class="bodytext">However, this returns:</p>
+<p class="commandtext">[( <maple> )<br/> ( <redMaple> )<br/> ( <oak> )<br/> ( <cactus> ) ]</p>
+
+<p class="bodytext">To understand what this query is doing, examine each constraint individually:</p>
+<ol class="listnumber">
+ <li class="listnumber"><code class="monospace">$s <rdf:type> <plant></code> returns all statements referring to a type of plant:<p class="listcontinuecommandtext">$s $p <br/><maple> <plant> <br/><redMaple> <plant> <br/><oak> <plant> <br/><cactus> <plant></p>
+ </li>
+ <li class="listnumber"><code class="monospace">$s <urn:leaves> $o</code> (before the <code class="monospace">exclude</code> operator is applied) returns all statements which match the predicate <code class="monospace"><leaves></code>:<p class="listcontinuecommandtext">$s $o<br /><maple> 'green'<br /><redMaple> 'red'<br /><oak> 'green'</p>
+ </li>
+ <li class="listnumber"><code class="monospace">exclude($s <urn:leaves> $o)</code> returns all statements which do not match the predicate <code class="monospace"><leaves></code>:<p class="listcontinuecommandtext">$s $o <br/><maple> <plant> <br/><redMaple> <plant> <br/><oak> <plant> <br/><cactus> <plant> <br/><cactus> 'yellow' </p>
+ </li>
+</ol>
+<p class="bodytext">Combining the two results (using <code class="monospace">and</code>), leads to all the subjects satisfng both constraints. This is incorrect. The required solution can be found if the <code class="monospace">minus</code> operator is used instead:</p>
+<p class="commandtext">select $s<br />from ...<br />where $s <rdf:type> <plant> <br/>minus $s <leaves> $o ;</p>
+<p class="bodytext">In this case the <code class="monospace">minus</code> operator will remove all statements matching the specified constraint, rather than joining to all statements which do not match the specified constraint (which is the operation of <code class="monospace">and exclude</code>). </p>
+
+
+<a name="o190"></a><h3 class="heading3">order by Clause</h3>
+<p class="bodytext">Optionally sorts the results of a <code class="monospace"><a id="h207_2" class="documentlinktemplate" title="select" href="187.htm" target="_self">select</a></code> command according to the variables specified.</p>
+<p class="bodytext">The following example sorts the results numerically by rating (assuming ratings can be parsed as numbers), then alphabetically by author for documents of equal rating.</p>
+<p class="commandtext">... order by $rating $title;</p>
+<p class="bodytext">The suffixes <code class="monospace">asc</code> and <code class="monospace">desc</code> may be used to override the default sort ordering for a variable.</p>
+<p class="bodytext">The following example sorts the results such that low ratings display first, and then alphabetically by author for documents of equal rating.</p>
+<p class="commandtext">... order by $rating asc $author;</p>
+<a name="o191"></a><h3 class="heading3">limit Clause</h3>
+<p class="bodytext">Optionally limits the query result to a specified non-negative number of rows.</p>
+<p class="bodytext">When using <code class="monospace">limit</code>, it is advisable to use the <code class="monospace"><a id="h219_2" class="documentlinktemplate" title="order by Clause" href="187.htm#o190" target="_self">order by</a></code> clause to constrain the result rows into a unique order. Otherwise you do not know which rows are returned. For example, if you limit a result to 10 rows without specifying an order, you do not know which 10 rows are returned.</p>
+<a name="o192"></a><h3 class="heading3">offset Clause</h3>
+<p class="bodytext">Optionally skips a non-negative number of rows at the beginning of a query result. The use of <code class="monospace">offset</code> usually accompanies a <code class="monospace"><a id="h221_2" class="documentlinktemplate" title="limit Clause" href="187.htm#o191" target="_self">limit</a></code> clause, making it possible to page through results.</p>
+<p class="bodytext">As with <code class="monospace">limit</code>, it is advisable to use the <code class="monospace"><a id="h219_3" class="documentlinktemplate" title="order by Clause" href="187.htm#o190" target="_self">order by</a></code> clause to constrain the result rows into a unique order.</p>
+<p class="bodytext">For examples and explanations of complete queries, see the <a id="h666" class="documentlinktemplate" title="Basic iTQL Operations" href="230.htm" target="_self">Issuing iTQL Commands section</a>.</p>
+<a name="o193"></a><h3 class="heading3">subquery Function</h3>
+<p class="bodytext">Used to nest <code class="monospace"><a id="h207_3" class="documentlinktemplate" title="select" href="187.htm" target="_self">select</a></code> commands. Subqueries nest inside <code class="monospace">select</code> by binding variables in the subquery <code class="monospace"><a id="h1321_2" class="documentlinktemplate" title="where Clause" href="187.htm#o197" target="_self">where</a></code> clause to the outer <code class="monospace"><a id="h1298_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code> clause.</p>
+<p class="bodytext">In the following example the value of <code class="monospace">$vcard</code> is bound to the inner query. The outer result set contains nested result sets for each subquery.</p>
+<p class="commandtext">select $vcard $fn <br /> subquery( select $title <br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title<br /> order by $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> order by $fn;</p>
+<p class="bodytext">The above example produces the following XML output from a SOAP call:</p>
+<p class="commandtext"><?xml version="1.0"?><br /><answer xmlns="http://tucanatech.com/tql#"><br /> <query><br /> <variables><br /> <vcard/><br /> <fn/><br /> <k0/><br /> </variables><br /> <solution><br /> <vcard resource="http://qqq.com/staff/superman"/><br /> <fn>Superman</fn><br /> <k0><br /> <variables><br /> <title/><br /> </variables><br /> </k0><br /> </solution><br /> <solution><br /> <vcard resource="http://qqq.com/staff/spiderman"/><br /> <fn>Peter Parker</fn><br /> <k0><br /> <variables><br /> <title/><br /> </variables><br /> <solution><br /> <title>Super Hero</title><br /> </solution><br /> <solution><br /> <title>PO2</title><br /> </solution><br /> </k0><br /> </solution><br /> <solution><br /> <vcard resource="http://qqq.com/staff/corky"/><br /> <fn>Corky Crystal</fn><br /> <k0><br /> <variables><br /> <title/><br /> </variables><br /> <solution><br /> <title>Computer Officer Class 3</title><br /> </solution><br /> </k0><br /> </solution><br /> </query><br /></answer></p>
+<a name="o194"></a><h3 class="heading3">count Function</h3>
+<p class="bodytext">Similar to <code class="monospace"><a id="h211_2" class="documentlinktemplate" title="subquery Function" href="187.htm#o193" target="_self">subquery</a></code> except that it only returns a dummy variable with value of the total row count of the inner query. See the <code class="monospace"><a id="h1320" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code><a id="h1320_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self"> clause section</a> for a description of dummy variables. For example:</p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn ;</p>
+<p class="bodytext">The above example returns the following:</p>
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"<br />vcard=http://qqq.com/staff/spiderman fn="Peter Parker" k0="2"<br />vcard=http://qqq.com/staff/superman fn="Superman" k0="0"</p>
+<a name="o2776"></a><h3 class="heading3">having Clause</h3>
+<p class="bodytext">The <code class="monospace">having</code> clause applies a constraint to a dummy variable that results from a <code class="monospace"><a id="h1323" class="documentlinktemplate" title="subquery Function" href="187.htm#o193" target="_self">subquery</a></code> in a <code class="monospace"><a id="h1320_3" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code><a id="h1320_4" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self"> clause</a> of a query. These variables are of the form <code class="monospace">$k0</code>, <code class="monospace">$k1</code>, <code class="monospace">$k2</code>, … <code class="monospace">$kn</code> and only hold numerical values. See the <code class="monospace"><a id="h1320_5" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code><a id="h1320_6" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self"> clause section</a> for a description of dummy variables.</p>
+<p class="bodytext">There are four special predicates that can be used to perform arithmetic comparisons in the <code class="monospace">having</code> clause, as outlined in the following table.</p>
+<table width="450" cellpadding="2" cellspacing="0" border="0" style="border-collapse:collapse">
+<tr align="left" valign="top">
+<td width="294"><p class="tableheading">Predicate</p>
+</td>
+<td width="156"><p class="tableheading">Arithmetic Operation</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://tucana.org/tucana#occurs</code></p>
+</td>
+<td width="156"><p class="tablebodytext">=</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://tucana.org/tucana#occursMoreThan</code></p>
+</td>
+<td width="156"><p class="tablebodytext">></p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://tucana.org/tucana#occursLessThan</code></p>
+</td>
+<td width="156"><p class="tablebodytext"><</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://tucana.org/tucana#notOccurs</code></p>
+</td>
+<td width="156"><p class="tablebodytext">?</p>
+</td>
+</tr>
+
+</table>
+<p class="bodytext">Expanding on the example shown in the <code class="monospace"><a id="h1323_2" class="documentlinktemplate" title="subquery Function" href="187.htm#o193" target="_self">subquery</a></code> and <code class="monospace"><a id="h733_2" class="documentlinktemplate" title="count Function" href="187.htm#o194" target="_self">count</a></code> sections, the following query restricts the result to those with a count of 1:</p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> having $k0 <http://tucana.org/tucana#occurs><br /> '1.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+<p class="bodytext">The above example returns:</p>
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"</p>
+<p class="bodytext">Similarly, to restrict the result to those with a count greater than 0 would be: </p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> having $k0 <http://tucana.org/tucana#occursMoreThan><br /> '0.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+<p class="bodytext">The above example returns:</p>
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"<br />vcard=http://qqq.com/staff/spiderman fn="Peter Parker" k0="2"</p>
+<p class="bodytext">The form of the constraint for the <code class="monospace">having</code> clause must be:</p>
+<p class="commandtext">$kx predicate value^^<http://www.w3.org/2001/XMLSchema#double></p>
+<p class="bodytext">Where p<code class="monospace">redicate</code> is one of the predicates from the above table.</p>
+<p class="bodytext">Note that compound constraints for the <code class="monospace">having</code> clause are not allowed. For example, the following query is <em class="emphasis">not</em> legal:</p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> having $k0 <http://tucana.org/tucana#occurs><br /> '0.0'^^<http://www.w3.org/2001/XMLSchema#double> <br /> or $k0 <http://tucana.org/tucana#occurs> <br /> '2.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+
+
+</td>
+</tr>
+<tr valign="bottom">
+<td>
+<br>
+<p class="toc">© 2001-2005 Northrop Grumman Corporation. Some rights reserved.</p>
+</td>
+</tr>
+</table>
+</body>
+</html>
+
+
+
Added: trunk/docs/oldSite/187.htm.r91
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--- trunk/docs/oldSite/187.htm.r91 2006-12-08 00:07:07 UTC (rev 146)
+++ trunk/docs/oldSite/187.htm.r91 2006-12-08 00:08:59 UTC (rev 147)
@@ -0,0 +1,296 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
+"http://www.w3.org/TR/html4/loose.dtd">
+<html>
+<head>
+<title> select </title>
+<link rel="icon" type="text/png"
+href="./media/images/icons/siteicon.png" />
+<link rel="shortcut icon" type="text/png" href="siteicon.png" />
+
+<meta name="author" content="Tom Adams" />
+<meta name="copyright" content="Copyright © 2003, Kowari Project" />
+<meta name="robots" content="all" />
+<meta name="description" content="Mulgara Project Home" />
+<meta name="keywords" content="select, mulgara project, metadata, metastore, metadatabase, datastore, database, scaleable, scalable, transaction, java, open source,homepage" />
+<meta name="location" content="Global" />
+<meta name="document-distribution" content="Global" />
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+<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
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+<meta http-equiv="language" content="English" />
+<meta http-equiv="window-target" content="_top" />
+
+<meta name="DC.Title" content="mulgara : semantic store" />
+<meta name="DC.Creator" content="Tom Adams" />
+<meta name="DC.Creator.Address" content="http://www.adams.id.au/tom/index.php" />
+<!--<meta name="DC.Contributor" content="Andrew Newman" />-->
+<meta name="DC.Subject" content="Mulgara Project Home" />
+<meta name="DC.Description" content="Mulgara Project Home" />
+<meta name="DC.Date.Created" scheme="iso8601" content="2003-09-22" />
+<meta name="DC.Modified" scheme="iso8601" content="2003-09-22" />
+<meta name="DC.Language" scheme="rfc1766" content="en" />
+<meta name="DC.Rights" scheme="URI" content="http://www.kowari.org/about/index.php#copyright" />
+<meta name="DC.Type" content="Text.Homepage.Personal" />
+<meta name="DC.Identifier" scheme="URI" content="http://mulgara.org/" />
+
+<meta name="Generator" content="AITPublish" />
+
+<link rel="stylesheet" href="mulgara_stylesheet.css">
+<!-- <link rel="stylesheet" href="44.css"> -->
+<base target="BODY">
+</head>
+<body>
+<table border="0" width="100%">
+<tr valign="top">
+<td width="80%">
+<table cellpadding="0" cellspacing="0" border="0">
+<tr valign="top">
+<td width= "18">
+<p class="prevnextbutton"><a href="186.htm" target="_self"><img src="previous.gif" alt="Previous Topic" height="25px" width="23px" vspace="2" hspace="2" align="bottom" border="0" /></a></p></td>
+<td width= "18">
+<p class="prevnextbutton"><a href="195.htm" target="_self"><img src="next.gif" alt="Next Topic" height="25px" width="23px" vspace="2" hspace="2" align="bottom" border="0" /></a></p></td>
+</tr>
+</table>
+<h2 class="heading2">select</h2>
+<p class="bodytext">Issues queries to Mulgara servers and displays the corresponding results. The command consists of a sequence of <code class="monospace"><a id="h217" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code>, <code class="monospace"><a id="h218" class="documentlinktemplate" title="from Clause" href="187.htm#o189" target="_self">from</a></code>, and <code class="monospace"><a id="h206" class="documentlinktemplate" title="where Clause" href="187.htm#o197" target="_self">where</a></code> clauses; and may optionally include <code class="monospace"><a id="h219" class="documentlinktemplate" title="order by Clause" href="187.htm#o190" target="_self">order by</a></code>, <code class="monospace"><a id="h220" class="documentlinktemplate" title="offset Clause" href="187.htm#o192" target="_self">offset</a></code> and <code class="monospace"><a id="h221" class="documentlinktemplate" title="limit Clause" href="187.htm#o191" target="_self">limit</a></code> clauses. With all clauses present, the general syntax is as follows:</p>
+<p class="commandtext">select columns from models where constraints order by variables limit count offset count;</p>
+<p class="bodytext">The purpose of the <code class="monospace">select</code> command is to find values for some set of variables that satisfy the specified constraints. All variable names start with a dollar sign (<code class="monospace">$)</code>, for example <code class="monospace">$x</code> or <code class="monospace">$title</code>.</p>
+<table cellpadding="0" cellspacing="0" border="0">
+<tr valign="top">
+<td width= "226.8">
+<p class="relatedheading">In This Section</p><p class="relateditem"><a href="187.htm#o188" target="_self">select Clause</a></p><p class="relateditem"><a href="187.htm#o189" target="_self">from Clause</a></p><p class="relateditem"><a href="187.htm#o197" target="_self">where Clause</a></p><p class="relateditem"><a href="187.htm#o190" target="_self">order by Clause</a></p><p class="relateditem"><a href="187.htm#o191" target="_self">limit Clause</a></p><p class="relateditem"><a href="187.htm#o192" target="_self">offset Clause</a></p><p class="relateditem"><a href="187.htm#o193" target="_self">subquery Function</a></p><p class="relateditem"><a href="187.htm#o194" target="_self">count Function</a></p><p class="relateditem"><a href="187.htm#o2776" target="_self">having Clause</a></p></td>
+<td width= "226.8">
+<p class="relatedheading">See Also</p><p class="relateditem"><a href="271.htm" target="_self">iTQL Commands</a></p><p class="relateditem"><a href="170.htm" target="_self">alias</a></p><p class="relateditem"><a href="171.htm" target="_self">backup</a></p><p class="relateditem"><a href="223.htm" target="_self">comment (#)</a></p><p class="relateditem"><a href="174.htm" target="_self">commit</a></p><p class="relateditem"><a href="176.htm" target="_self">create</a></p><p class="relateditem"><a href="178.htm" target="_self">delete</a></p><p class="relateditem"><a href="179.htm" target="_self">drop</a></p><p class="relateditem"><a href="180.htm" target="_self">execute</a></p><p class="relateditem"><a href="181.htm" target="_self">help</a></p><p class="relateditem"><a href="182.htm" target="_self">insert</a></p><p class="relateditem"><a href="183.htm" target="_self">load</a></p><p class="relateditem"><a href="184.htm" target="_self">quit</a></p><p class="relateditem"><a href="185.htm" target="_self">restore</a></p><p class="relateditem"><a href="186.htm" target="_self">rollback</a></p><p class="relateditem"><a href="195.htm" target="_self">set</a></p></td>
+</tr>
+</table>
+
+<a name="o188"></a><h3 class="heading3">select Clause</h3>
+<p class="bodytext">Specifies the variables to solve for and their order in the result. For example:</p>
+<p class="commandtext">select $title $author $date ...</p>
+<p class="bodytext">Constant resource or literal values may be part of a <code class="monospace">select</code> clause. In these cases, dummy variable names (<code class="monospace">$k0</code>, <code class="monospace">$k1</code>, <code class="monospace">$k2</code>, … <code class="monospace">$kn</code>) are created for the constant values.</p>
+<p class="bodytext">The following example returns three columns: <code class="monospace">$k0</code>, <code class="monospace">$x</code> and <code class="monospace">$k1</code> where the values of <code class="monospace">$k0</code> and <code class="monospace">$k1</code> for every solution are the literal value <code class="monospace">foo</code> and the resource value <code class="monospace">http://www.site.domain.net</code> respectively.</p>
+<p class="commandtext">select 'foo' $x <http://www.site.domain.net> ...</p>
+<a name="o189"></a><h3 class="heading3">from Clause</h3>
+<p class="bodytext">Specifies the model to query. For example:</p>
+<p class="commandtext">... from <rmi://mysite.com/server1#model1> ...</p>
+<p class="bodytext">Because models are sets of statements, it is logical to compose them using set operations. The <code class="monospace">from </code>clause permits set union using the <code class="monospace">or</code> operator and set intersection using the <code class="monospace">and</code> operator, with parentheses used to control association.</p>
+<a name="o3149"></a>
+<p class="bodytext">The following example queries only the statements appearing in all three models. </p>
+<p class="commandtext">... from <rmi://mysite.com/server1#model1> and <rmi://mysite.com/server1#model2><br /> and <rmi://mysite.com/server1#model3> ...</p>
+<a name="o197"></a><h3 class="heading3">where Clause</h3>
+<p class="bodytext">The <code class="monospace">where</code> clause is usually the largest and most detailed clause of the <code class="monospace"><a id="h207" class="documentlinktemplate" title="select" href="187.htm" target="_self">select</a></code> command. It specifies the constraints that must be satisfied by the variable values in each solution. A constraint is a sequence of subject, predicate and object that represents an RDF statement. Each of the three positions is either a constant value (a resource or a literal) or a variable. The Mulgara server finds values for any variables such that the resulting statement is present in the model that was specified in the preceding <code class="monospace"><a id="h1326" class="documentlinktemplate" title="from Clause" href="187.htm#o189" target="_self">from</a></code> clause.</p>
+<p class="bodytext">For example, the following <code class="monospace">where</code> clause constrains that in all solutions, the value of <code class="monospace">$title</code> is the title of the resource referred to in <code class="monospace">$document</code>.</p>
+<p class="commandtext">... where $document <dc:title> $title ...</p>
+<p class="bodytext">Constraints may be composed using <code class="monospace">and</code> and <code class="monospace">or</code> operations, with parentheses to control association.</p>
+<p class="bodytext">The following example returns every document with a title, an author and a subject of either botany or zoology. Documents without a known title or author are not returned.</p>
+<p class="commandtext">... where $document <dc:title> $title and $document <dc:creator> $author <br /> and ($document <dc:subject> 'botany' or $document <dc:subject> 'zoology') ...</p>
+<a name="o1530"></a><h4 class="heading4">in Specifier</h4>
+<p class="bodytext">Constraints may optionally contain an <code class="monospace">in</code> specifier to resolve the constraint against the statements in a specified model, rather than the one specified in the <code class="monospace"><a id="h1303" class="documentlinktemplate" title="from Clause" href="187.htm#o189" target="_self">from</a></code> clause.</p>
+<p class="bodytext">The following example constrains the result by titles in the <code class="monospace">#books</code> model rather than the one specified in the <code class="monospace">from</code> clause.</p>
+<p class="commandtext">... where $document <dc:title> $title in <rmi://mysite.com/server1#books> ...</p>
+<a name="o1531"></a><h4 class="heading4">Assigning a Value to a Variable (mulgara:is)</h4>
+<p class="bodytext">Constraints may also assign a value to a variable rather then querying for it. The special property <code class="monospace">http://mulgara.org/mulgara#is </code>(or the aliased form <code class="monospace"><mulgara:is></code>) can be used with a variable as its subject and a non-variable value as its object. This assigns the non-variable value to the variable.</p>
+<p class="bodytext">The following example results in every document authored by Mendel about genetics, or by Mendeleev about chemistry.</p>
+<p class="commandtext">... where $document <dc:title> $title and $document <dc:creator> $author <br /> and $document <dc:subject> $subject <br /> and (($author <mulgara:is> 'Mendel' and $subject <mulgara:is> 'genetics' ) <br /> or ($author <mulgara:is> 'Mendeleev' and $subject <mulgara:is> 'chemistry')) ...</p>
+<a name="o1532"></a><h4 class="heading4">Traversing a Graph (walk Function)</h4>
+<p class="bodytext">Traversing a graph allows a query to return values, based on a predicate, by following up or down a hierarchy of statements. In a schema language such as RDFS, these hierarchies are expressed as a sub-class or sub-property predicate. Traversing a graph is performed with the <code class="monospace">walk</code> function within a <code class="monospace"><a id="h1321" class="documentlinktemplate" title="where Clause" href="187.htm#o197" target="_self">where</a></code> clause.</p>
+<p class="bodytext">The syntax of the <code class="monospace">walk</code> function is either:</p>
+<p class="listcontinuecommandtext">walk ($subject_variable <predicate_URI> <object_URI> and<br />$subject_variable <predicate_URI> $object_variable)</p>
+<p class="listcontinue">or</p>
+<p class="listcontinuecommandtext">walk (<subject_URI> <predicate_URI> $object_variable and<br />$subject_variable <predicate_URI> $object_variable)</p>
+<p class="bodytext">The <code class="monospace">walk</code> function must be bound to a <code class="monospace"><a id="h1298" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code> clause using the same triple pattern that matches the second parameter. For example:</p>
+<p class="commandtext">select $subject <predicate_URI> $object<br />...<br />where walk ($subject <predicate_URI> <object_URI> and<br />$subject <predicate_URI> $object);</p>
+<p class="bodytext">An example of <code class="monospace">walk</code> is demonstrated using the following statements:</p>
+<p class="commandtext">[ ( <kangroos>, <rdfs:subClassOf>, <marsupials> )<br /> ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br /> ( <placental-mammals>, <rdfs:subClassOf>, <mammals> )<br /> ( <mammals>, <rdfs:subClassOf>, <vertebrates> ) ]</p>
+<p class="bodytext">To query a set of statements in the hierarchy ending with <code class="monospace"><vertebrates></code> as an object:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where walk($subject <rdfs:subClassOf> <vertebrates><br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">Working from the bottom up, the system:</p>
+<ul class="listbullet"><li class="listbullet">Matches <code class="monospace">( <mammals>, <rdfs:subClassOf>, <vertebrates> )</code> and then substitutes <code class="monospace"><mammals></code> for <code class="monospace"><vertebrates></code> in the constraints.</li><li class="listbullet">Attempts to match for the triples <code class="monospace">( *, <rdfs:subClassOf>, <mammals> )</code>.</li><li class="listbullet">Then matches for <code class="monospace">( <marsupials>, <rdfs:subClassOf>, <mammals> )</code> and <code class="monospace">( <placental-mammals>, <rdfs:subClassOf>, <mammals> )</code>.</li><li class="listbullet">Then matches for <code class="monospace">( *, <rdfs:subClassOf>, <marsupials> )</code> and (<code class="monospace"> *, <rdfs:subClassOf>, <placental-mammals> )</code> and so on.</li></ul><p class="bodytext">The result of the query is:</p>
+<p class="commandtext">[ ( <mammals>, <rdfs:subClassOf>, <vertebrates> )<br /> ( <placental-mammals>, <rdfs:subClassOf>, <mammals> )<br /> ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br /> ( <kangaroos>, <rdfs:subClassOf>, <marsupials> ) ]</p>
+<p class="bodytext">You can also traverse down the graph following the hierarchy. For example:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where walk(<kangaroos> <rdfs:subClassOf> $object<br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">This returns:</p>
+<p class="commandtext">[ ( <kangaroos>, <rdfs:subClassOf>, <marsupials> )<br /> ( <marsupials>, <rdfs:subClassOf>, <mammals> )<br /> ( <mammals>, <rdfs:subClassOf>, <vertebrates> ) ]</p>
+<a name="o1535"></a><h4 class="heading4">Transitive Closure (trans Function)</h4>
+<p class="bodytext">Transitive closure provides the ability to express a function that generates new statements. Normally, transitive closure produces both existing and new statements. The <code class="monospace">trans</code> function in iTQL<sup class="superscript">TM</sup> only produces new statements, statements that did not exist in the model before it was executed. The <code class="monospace">trans</code> function can be further constrained by limiting which statements are inferred and by giving it a starting or termination point.</p>
+<p class="bodytext">The simplest form of the <code class="monospace">trans</code> function defines a predicate to operate on:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">This generates a new statement, <code class="monospace">$x <rdfs:subClassOf> $z</code>, when it finds two statements that match the pattern <code class="monospace">$x <rdfs:subClassOf> $y</code> and <code class="monospace">$y <rdfs:subClassOf> $z</code>.</p>
+<p class="bodytext">For example, consider the following set of statements:</p>
+<p class="commandtext">[ (<mammals>, <rdfs:subClassOf>, <vertebrates>)<br /> (<eats-leaves>, <rdfs:subPropertyOf>, <herbivore>)<br /> (<marsupials>, <rdfs:subClassOf>, <mammals>)<br /> (<placental-mammals>, <rdfs:subClassOf>, <mammals>)<br /> (<elephants>, <rdfs:subClassOf>, <placental-mammals>)<br /> (<kangaroos>, <rdfs:subClassOf>, <marsupials>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <kangaroos>) ]</p>
+<p class="bodytext">As a tree it looks as follows:</p>
+<p class="bodytext"><img src="1536.gif" alt="Transitive Closure" height="273" width="252" vspace="0" hspace="0" align="bottom" border="0" /></p>
+<p class="bodytext">Based on the constraint in the query, the first and third statements match the pattern <code class="monospace">(<marsupials>, <rdfs:subClassOf>, <mammals>) and (<mammals>, <rdfs:subClassOf>, <vertebrates>)</code>. Therefore, the function generates the statement <code class="monospace">(<marsupials>, <rdfs:subClassOf>, <vertebrates>)</code>.</p>
+<p class="bodytext">Using the query across the existing set of statements produces the following new set of statements:</p>
+<p class="commandtext">[ (<code class="monospace"><marsupials>, <rdfs:subClassOf>, <vertebrates></code>)<br /> (<kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<placental-mammals>, <rdfs:subClassOf>, <<code class="monospace">vertebrates></code>)<br /> (<elephants>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<elephants>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <marsupials>) ]</p>
+<p class="bodytext">To provide the results expected from a transitive closure function you would union together these newly generated statements with the original base set of statements, using the following query:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($subject <rdfs:subClassOf> $object)<br />or $subject <rdfs:subClassOf> $object;</p>
+<p class="bodytext">You can further restrict the <code class="monospace">trans</code> function to a sub-set of statements, as shown in the following example.</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($subject <rdfs:subClassOf> <mammals><br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">This produces new statements where the object in the inheritance tree begins with <code class="monospace"><mammals></code>, eliminating the statements derived from <code class="monospace"><vertebrates></code>. It produces the following:</p>
+<p class="commandtext">[ (<kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <mammals>)<br /> (<elephants>, <rdfs:subClassOf>, <mammals>)<br /> (<red-kangroos>, <rdfs:subClassOf>, <marsupials>) ]</p>
+<p class="bodytext">To get the full transitive closure, the newly inferred statements are unioned with the base statements. To only return the sub-graph from <code class="monospace"><mammals></code> we can add the results from a <code class="monospace"><a id="h1537" class="documentlinktemplate" title="Traversing a Graph (walk Function)" href="187.htm#o1532" target="_self">walk</a></code> function:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans($xxx <rdfs:subClassOf> <mammals><br />and $subject <rdfs:subClassOf> $object) or<br />walk($subject <rdfs:subClassOf> <mammals><br />and $subject <rdfs:subClassOf> $object);</p>
+<p class="bodytext">To generate the statements to <code class="monospace"><marsupials></code> you can constrain the subject in the function instead:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> $object<br />...<br />where trans(<marsupials> <rdfs:subClassOf> $object<br />and $subject <rdfs:subClassOf> $object) ;</p>
+<p class="bodytext">This produces:</p>
+<p class="commandtext">[ <marsupials>, <rdfs:subClassOf>, <vertebrates>) ]</p>
+<p class="bodytext">The <code class="monospace">trans</code> function also allows you to limit what is inferred by dropping the second constraint within the <code class="monospace">trans</code> definition. For example, to infer only direct statements from <code class="monospace"><vertebrates></code>:</p>
+<p class="commandtext">select $subject <rdfs:subClassOf> <<code class="monospace">vertebrates</code>><br />...<br />where trans($subject <rdfs:subClassOf> <<code class="monospace">vertebrates</code>>)</p>
+<p class="bodytext">Which produces:</p>
+<p class="commandtext">[ (<marsupials>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<red-kangaroos>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<placental-mammals>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>)<br /> (<elephants>, <rdfs:subClassOf>, <<code class="monospace">vertebrates</code>>) ]</p>
+<p class="bodytext">Likewise, you can also make the subject in the <code class="monospace">trans</code> constraint a constant and the object a variable.</p>
+<a name="o2768"></a><h4 class="heading4">exclude Function</h4>
+<p class="bodytext">The <code class="monospace">exclude</code> function allows you to select all statements whose properties are the inverse of a given constraint. Normal constraints match against the graph with the constraints you provide. Constraints enclosed in an <code class="monospace">exclude</code> function return the values in the graph that are not the constraints provided. This allows you to build queries to ask questions such as: "find me all the known plants stored, with leaves that are not green" or "find me all the American states stored that are not Alabama".</p>
+<p class="bodytext">Using the following statements as an example:</p>
+<p class="commandtext">[ (<maple>, <leaves>, 'green')<br /> (<redMaple>, <leaves>, 'red')<br /> (<oak>, <leaves>, 'green')<br /> (<cactus>, <prickles>, 'yellow') ]</p>
+<p class="bodytext">You wish to find all plants that do not have leaves. The following query:</p>
+<p class="commandtext">select $s $p $o<br />...<br />where exclude($s <leaves> $o) <br />and ($s $p $o);</p>
+<p class="bodytext">Returns:</p>
+<p class="commandtext">[ (<cactus>, <prickles>, 'yellow') ]</p>
+<p class="bodytext">Unless your model is very small, the <code class="monospace">exclude</code> function by itself is rarely useful. For example, the following query:</p>
+<p class="commandtext">select $s $p $o<br />...<br />where exclude($s <leaves> 'green')<br />and $s $p $o;</p>
+<p class="bodytext">Returns:</p>
+<p class="commandtext">[ (<cactus>, <prickles>, 'yellow')<br /> (<redMaple), <leaves>, 'red' ]</p>
+<p class="bodytext">As this returns all statements that do not have the predicate <code class="monospace"><leaves></code> and the object value 'green', if a statement exists where <em class="emphasis">either</em> of these columns do not match, it is returned. If you want to find all the things that have leaves that are not green you need to perform the following query:</p>
+<p class="commandtext">select $s<br />...<br />where $s <urn:leaves> $o <br />and exclude($s $p 'green');</p>
+<p class="bodytext">To understand what this query is doing, examine each constraint individually:</p>
+<ol class="listnumber"><li class="listnumber"><code class="monospace">$s <urn:leaves> $o</code> returns all statements with the predicate <code class="monospace"><leaves></code>:<p class="listcontinuecommandtext">$s $o<br /><maple> 'green'<br /><redMaple> 'red'<br /><oak> 'green'</p>
+</li><li class="listnumber"><code class="monospace">exclude($s $p 'green')</code> returns all statements that do not have the object value 'green':<p class="listcontinuecommandtext">$s $p<br /><redMaple> <leaves><br /><cactus> <prickles></p>
+</li></ol><p class="bodytext">Combining these two results (using <code class="monospace">and</code>), only one statement satisfies all constraints and the query returns the variable (<code class="monospace">$s</code>) in the <code class="monospace"><a id="h217_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code> clause:</p>
+<p class="commandtext">[ (<redMaple>) ]</p>
+<p class="bodytext">Rarely do graphs contain just one easily defined set of statement. Extending the base set of statements with overlapping predicates for our example:</p>
+<p class="commandtext">[ (<maple>, <type>, <plant>)<br /> (<redMaple>, <type>, <plant>)<br /> (<oak>, <type>, <plant>)<br /> (<cactus>, <type>, <plant>)<br /> (<maple>, <leaves>, 'green')<br /> (<redMaple>, <leaves>, 'red')<br /> (<oak>, <leaves>, 'green')<br /> (<cactus>, <prickles>, 'yellow') <br /> (<binderRefill>, <leaves>, '50') ]</p>
+<p class="bodytext">Using the previous query:</p>
+<p class="commandtext">select $s<br />...<br />where $s <urn:leaves> $o <br />and exclude($s $p 'green');</p>
+<p class="bodytext">Returns:</p>
+<p class="commandtext">[ (<maple>)<br /> (<redMaple>)<br /> (<oak>)<br /> (<binderRefill>) ]</p>
+<p class="bodytext">Examining each constraint individually again:</p>
+<ol class="listnumber"><li class="listnumber"><code class="monospace">$s <urn:leaves> $o</code> returns all statements with the predicate <code class="monospace"><leaves></code>:<p class="listcontinuecommandtext">$s $o<br /><maple> 'green'<br /><redMaple> 'red'<br /><oak> 'green'<br /><binderRefill> '50'</p>
+</li><li class="listnumber"><code class="monospace">exclude($s $p 'green')</code> returns all statements that do not have the object value 'green':<p class="listcontinuecommandtext">$s $p<br /><maple> <type><br /><redMaple> <type><br /><oak> <type><br /><cactus> <type><br /><redMaple> <leaves><br /><cactus> <prickles><br /><binderRefill> <leaves></p>
+</li></ol><p class="bodytext">Combining the <code class="monospace">$s</code> column from each result of the constraints, leads to the result.</p>
+<p class="bodytext">You usually need to restrict the <code class="monospace">exclude</code> constraint. In the previous examples, you only want to query things that are plants and not the entire graph. It is also preferable that the results from these constraints exist as real statements in a graph. To restrict the constraints so they only return things in the graph, the variables must be bound to the relevant positions.</p>
+<p class="bodytext">For example, the following query:</p>
+<p class="commandtext"><code class="monospace">select $s $p $o<br />...<br />where $s <urn:leaves> $o <br />and exclude($s $p 'green') <br />and $s $p $o;</code></p>
+<p class="bodytext">Returns:</p>
+<p class="commandtext"><code class="monospace">[ (<redMaple>, <leaves>, 'red')<br /> (<binderRefill>, <leaves>, '50') ]</code></p>
+<p class="bodytext">Note that the query still has not restricted the type of the object. To only query plants, the following query:</p>
+<p class="commandtext"><code class="monospace">select $s $p $o<br />...<br />where $s <urn:leaves> $o <br />and exclude($s $p 'green') <br />and $s $p $o<br />and $s <type> <plant> ;</code></p>
+<p class="bodytext">Returns:</p>
+<p class="commandtext"><code class="monospace">[ (<redMaple>, <leaves>, 'red') ]</code></p>
+<a name="o2769"></a><h5 class="heading5">Standard Queries</h5>
+<p class="bodytext">The variable names used in the <code class="monospace">exclude</code> function are not bound by other constraints, including the <code class="monospace"><code class="monospace"><a id="h2772" class="documentlinktemplate" title="Assigning a Value to a Variable (mulgara:is)" href="187.htm#o1531" target="_self"><mulgara:is></a></code></code> operation. All other operations match statements in the graph. So it is not the same thing as replacing positively matching values from the graph and assigning these values to the <code class="monospace">exclude</code> function. The variable names used in the <code class="monospace">exclude</code> function and other operations are only used to join the column values from the results of each constraint.</p>
+<p class="bodytext">For example, the query:</p>
+<p class="commandtext"><code class="monospace">select $s $p $o<br />...<br />where exclude($s $p 'green')<br />and $p <mulgara:is> <leaves><br />and $s $p $o;</code></p>
+<p class="bodytext">Results in all the statements that do not have the object value 'green', combined with all the statements with the predicate <code class="monospace"><leaves></code>:</p>
+<p class="commandtext"><code class="monospace">[ (<redMaple>, <leaves>, 'red')<br /> (<binderRefill>, <leaves>, '50') ]</code></p>
+<p class="bodytext">Note that this is not the same as:</p>
+<p class="commandtext"><code class="monospace">select $s $p $o<br />...<br />where exclude ($s <urn:leaves> 'green')<br />and $p <mulgara:is> <leaves><br />and $s $p $o;</code></p>
+<p class="bodytext">Which returns:</p>
+<p class="commandtext"><code class="monospace">[ (<maple>, <leaves>, 'green')<br /> (<oak>, <leaves>, 'green') ]</code></p>
+<a name="o2770"></a><h5 class="heading5">exclude($s $p $o)</h5>
+<p class="bodytext"><code class="monospace">exclude</code> functions that only contain variables usually return no result. If joined to other constraints with <code class="monospace">and</code>, it will return no result. As stated above, this cannot be changed by using <code class="monospace"><a id="h2772_2" class="documentlinktemplate" title="Assigning a Value to a Variable (mulgara:is)" href="187.htm#o1531" target="_self"><mulgara:is></a></code> or other constraints. The only exception to this is when the <code class="monospace">exclude</code> function is used in a subquery or aggregate function. See the next section on subqueries for more details.</p>
+<p class="bodytext">For example, the following query returns no result.</p>
+<p class="commandtext"><code class="monospace">select $s $p $o<br />...<br />where exclude ($s $p $o)<br />and $o <mulgara:is> 'green'<br />and $s $p $o;</code></p>
+<a name="o2771"></a><h5 class="heading5">Subqueries</h5>
+<p class="bodytext">Subqueries allow the results from one query to be used in another. That is, the values of the outer queries bind to the variables with the same name in the inner query. So a constraint such as <code class="monospace">exclude($s $p $o)</code>, which normally returns no result, could return results if used in a <code class="monospace"><code class="monospace"><a id="h211" class="documentlinktemplate" title="subquery Function" href="187.htm#o193" target="_self">subquery</a></code></code> or <code class="monospace"><a id="h733" class="documentlinktemplate" title="count Function" href="187.htm#o194" target="_self">count</a></code> function when any of the variables <code class="monospace">$s</code>, <code class="monospace">$p</code> or <code class="monospace">$o</code> are bound by the outer query.</p>
+<p class="bodytext">For example, the following query binds the <code class="monospace">$s</code> and <code class="monospace">$o</code> values of the internal query:</p>
+<p class="commandtext"><code class="monospace">select $s $o subquery(<br /> select $s2 $p2 $o2 <br /> ...<br /> where exclude($s $p2 $o) <br /> and $s $p2 $o2 <br /> and $s2 $p2 $o)<br />...<br />where $s <urn:type> $o ;</code></p>
+<p class="bodytext">The first result passes values to the internal <code class="monospace">subquery</code> where <code class="monospace">$s</code> is <code class="monospace"><maple></code> and <code class="monospace">$o</code> is <code class="monospace"><plant></code>. This causes the inner query to look like:</p>
+<p class="commandtext"><code class="monospace">select $s2 $p2 $o2 <br />...<br />where exclude(<maple> $p2 <plant>)<br />and <maple> $p2 $o2 <br />and $s2 $p2 <plant></code></p>
+<a name="o190"></a><h3 class="heading3">order by Clause</h3>
+<p class="bodytext">Optionally sorts the results of a <code class="monospace"><a id="h207_2" class="documentlinktemplate" title="select" href="187.htm" target="_self">select</a></code> command according to the variables specified.</p>
+<p class="bodytext">The following example sorts the results numerically by rating (assuming ratings can be parsed as numbers), then alphabetically by author for documents of equal rating.</p>
+<p class="commandtext">... order by $rating $title;</p>
+<p class="bodytext">The suffixes <code class="monospace">asc</code> and <code class="monospace">desc</code> may be used to override the default sort ordering for a variable.</p>
+<p class="bodytext">The following example sorts the results such that low ratings display first, and then alphabetically by author for documents of equal rating.</p>
+<p class="commandtext">... order by $rating asc $author;</p>
+<a name="o191"></a><h3 class="heading3">limit Clause</h3>
+<p class="bodytext">Optionally limits the query result to a specified non-negative number of rows.</p>
+<p class="bodytext">When using <code class="monospace">limit</code>, it is advisable to use the <code class="monospace"><a id="h219_2" class="documentlinktemplate" title="order by Clause" href="187.htm#o190" target="_self">order by</a></code> clause to constrain the result rows into a unique order. Otherwise you do not know which rows are returned. For example, if you limit a result to 10 rows without specifying an order, you do not know which 10 rows are returned.</p>
+<a name="o192"></a><h3 class="heading3">offset Clause</h3>
+<p class="bodytext">Optionally skips a non-negative number of rows at the beginning of a query result. The use of <code class="monospace">offset</code> usually accompanies a <code class="monospace"><a id="h221_2" class="documentlinktemplate" title="limit Clause" href="187.htm#o191" target="_self">limit</a></code> clause, making it possible to page through results.</p>
+<p class="bodytext">As with <code class="monospace">limit</code>, it is advisable to use the <code class="monospace"><a id="h219_3" class="documentlinktemplate" title="order by Clause" href="187.htm#o190" target="_self">order by</a></code> clause to constrain the result rows into a unique order.</p>
+<p class="bodytext">For examples and explanations of complete queries, see the <a id="h666" class="documentlinktemplate" title="Basic iTQL Operations" href="230.htm" target="_self">Issuing iTQL Commands section</a>.</p>
+<a name="o193"></a><h3 class="heading3">subquery Function</h3>
+<p class="bodytext">Used to nest <code class="monospace"><a id="h207_3" class="documentlinktemplate" title="select" href="187.htm" target="_self">select</a></code> commands. Subqueries nest inside <code class="monospace">select</code> by binding variables in the subquery <code class="monospace"><a id="h1321_2" class="documentlinktemplate" title="where Clause" href="187.htm#o197" target="_self">where</a></code> clause to the outer <code class="monospace"><a id="h1298_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code> clause.</p>
+<p class="bodytext">In the following example the value of <code class="monospace">$vcard</code> is bound to the inner query. The outer result set contains nested result sets for each subquery.</p>
+<p class="commandtext">select $vcard $fn <br /> subquery( select $title <br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title<br /> order by $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> order by $fn;</p>
+<p class="bodytext">The above example produces the following XML output from a SOAP call:</p>
+<p class="commandtext"><?xml version="1.0"?><br /><answer xmlns="http://mulgara.org/tql#"><br /> <query><br /> <variables><br /> <vcard/><br /> <fn/><br /> <k0/><br /> </variables><br /> <solution><br /> <vcard resource="http://qqq.com/staff/superman"/><br /> <fn>Superman</fn><br /> <k0><br /> <variables><br /> <title/><br /> </variables><br /> </k0><br /> </solution><br /> <solution><br /> <vcard resource="http://qqq.com/staff/spiderman"/><br /> <fn>Peter Parker</fn><br /> <k0><br /> <variables><br /> <title/><br /> </variables><br /> <solution><br /> <title>Super Hero</title><br /> </solution><br /> <solution><br /> <title>PO2</title><br /> </solution><br /> </k0><br /> </solution><br /> <solution><br /> <vcard resource="http://qqq.com/staff/corky"/><br /> <fn>Corky Crystal</fn><br /> <k0><br /> <variables><br /> <title/><br /> </variables><br /> <solution><br /> <title>Computer Officer Class 3</title><br /> </solution><br /> </k0><br /> </solution><br /> </query><br /></answer></p>
+<a name="o194"></a><h3 class="heading3">count Function</h3>
+<p class="bodytext">Similar to <code class="monospace"><a id="h211_2" class="documentlinktemplate" title="subquery Function" href="187.htm#o193" target="_self">subquery</a></code> except that it only returns a dummy variable with value of the total row count of the inner query. See the <code class="monospace"><a id="h1320" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code><a id="h1320_2" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self"> clause section</a> for a description of dummy variables. For example:</p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn ;</p>
+<p class="bodytext">The above example returns the following:</p>
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"<br />vcard=http://qqq.com/staff/spiderman fn="Peter Parker" k0="2"<br />vcard=http://qqq.com/staff/superman fn="Superman" k0="0"</p>
+<a name="o2776"></a><h3 class="heading3">having Clause</h3>
+<p class="bodytext">The <code class="monospace">having</code> clause applies a constraint to a dummy variable that results from a <code class="monospace"><a id="h1323" class="documentlinktemplate" title="subquery Function" href="187.htm#o193" target="_self">subquery</a></code> in a <code class="monospace"><a id="h1320_3" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code><a id="h1320_4" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self"> clause</a> of a query. These variables are of the form <code class="monospace">$k0</code>, <code class="monospace">$k1</code>, <code class="monospace">$k2</code>, … <code class="monospace">$kn</code> and only hold numerical values. See the <code class="monospace"><a id="h1320_5" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self">select</a></code><a id="h1320_6" class="documentlinktemplate" title="select Clause" href="187.htm#o188" target="_self"> clause section</a> for a description of dummy variables.</p>
+<p class="bodytext">There are four special predicates that can be used to perform arithmetic comparisons in the <code class="monospace">having</code> clause, as outlined in the following table.</p>
+<table width="450" cellpadding="2" cellspacing="0" border="0" style="border-collapse:collapse">
+<tr align="left" valign="top">
+<td width="294"><p class="tableheading">Predicate</p>
+</td>
+<td width="156"><p class="tableheading">Arithmetic Operation</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://mulgara.org/mulgara#occurs</code></p>
+</td>
+<td width="156"><p class="tablebodytext">=</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://mulgara.org/mulgara#occursMoreThan</code></p>
+</td>
+<td width="156"><p class="tablebodytext">></p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://mulgara.org/mulgara#occursLessThan</code></p>
+</td>
+<td width="156"><p class="tablebodytext"><</p>
+</td>
+</tr>
+<tr align="left" valign="top">
+<td width="294"><p class="tablebodytext"><code class="monospace">http://mulgara.org/mulgara#notOccurs</code></p>
+</td>
+<td width="156"><p class="tablebodytext">?</p>
+</td>
+</tr>
+
+</table>
+<p class="bodytext">Expanding on the example shown in the <code class="monospace"><a id="h1323_2" class="documentlinktemplate" title="subquery Function" href="187.htm#o193" target="_self">subquery</a></code> and <code class="monospace"><a id="h733_2" class="documentlinktemplate" title="count Function" href="187.htm#o194" target="_self">count</a></code> sections, the following query restricts the result to those with a count of 1:</p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> having $k0 <http://mulgara.org/mulgara#occurs><br /> '1.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+<p class="bodytext">The above example returns:</p>
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"</p>
+<p class="bodytext">Similarly, to restrict the result to those with a count greater than 0 would be: </p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> having $k0 <http://mulgara.org/mulgara#occursMoreThan><br /> '0.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+<p class="bodytext">The above example returns:</p>
+<p class="commandtext">vcard=http://qqq.com/staff/corky fn="Corky Crystal" k0="1"<br />vcard=http://qqq.com/staff/spiderman fn="Peter Parker" k0="2"</p>
+<p class="bodytext">The form of the constraint for the <code class="monospace">having</code> clause must be:</p>
+<p class="commandtext">$kx predicate value^^<http://www.w3.org/2001/XMLSchema#double></p>
+<p class="bodytext">Where p<code class="monospace">redicate</code> is one of the predicates from the above table.</p>
+<p class="bodytext">Note that compound constraints for the <code class="monospace">having</code> clause are not allowed. For example, the following query is <em class="emphasis">not</em> legal:</p>
+<p class="commandtext">select $vcard $fn <br /> count( select $title from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#TITLE> $title )<br /> from <rmi://mysite.com/server1#vcard> <br /> where $vcard <http://www.w3.org/2001/vcard-rdf/3.0#FN> $fn <br /> having $k0 <http://mulgara.org/mulgara#occurs><br /> '0.0'^^<http://www.w3.org/2001/XMLSchema#double> <br /> or $k0 <http://mulgara.org/mulgara#occurs> <br /> '2.0'^^<http://www.w3.org/2001/XMLSchema#double> ;</p>
+
+
+ </td>
+ <td width=20>
+ </td>
+ <td align="left">
+ <a href="http://www.opensource.org/docs/definition.php" title="Open Source Initiative" target="_blank"><img style="border:0;width:110px;height:95;" src="http://www.opensource.org/trademarks/opensource/web/opensource-110x95.png" alt="Open Source logo" /></a>
+
+
+</td>
+</tr>
+<tr valign="bottom">
+<td>
+<br>
+<p class="toc">© 2001-2004 Tucana Technologies, Inc. Some rights reserved.</p> <p class="toc">© 2006 The Mulgara Project. Some rights reserved.<br>Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "<a href="fdl.txt">GNU Free Documentation License</a>".</p>
+</td>
+</tr>
+</table>
+</body>
+</html>
+
+
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