[Mulgara-general] Inferencing

[Paul Gearon]

HI Jeff,

Mulgara isn't doing OWL at the moment.  I've reduced the priority on  
this while I get SPARQL working.

However, Mulgara does support RDFS.  This is performed via  
application of rules.  The rules need to be reapplied as new data is  
inserted.  We have plans to automate this, and optimize the  
reapplication of the rules, but for now they are stateless.

The inferencing docs were written before we had any RDFS or OWL  
support at all.  They simply describe queries which can construct the  
sorts of inferences you need.  These form a rudimentary basis for the  
rules that can infer for RDFS or OWL, though more is needed.  As  
such, you can use them if you specifically need to see certain  
statements, but they are a very manual mechanism for looking at your  
data.

To apply the RDFS rules, you load the rules into one model, and apply  
them to another.  The results can go into the same model the base  
statements are in, or they can go into a new model (if they go into a  
new model you will want to do all subsequent queries on the union of  
the base and inferred models.  Unions are performed with the "or"  
operation).

The RDFS Rules also require access to two "placeholder" models, which  
provide markers for the system to know to perform certain  
operations.  They don't actually take up any space.  These are built  
with:
create <rmi://localhost/server1#type> <mulgara:TypeModel>;
create <rmi://localhost/server1#prefix> <mulgara:PrefixModel>;

If you have your RDFS rules loaded into a model called "rdfs" and  
your base data in a model called "input", then you can generate new  
data to be inserted into a model called "output" via:

apply <rmi://localhost/server1#rdfs> to <rmi://localhost/ 
server1#input> <rmi://localhost/server1#output>;

The exact steps are in the file rules/example.itql.  The format of  
the rules files is described in rules/RuleFormat.txt.  The rule file  
for RDFS is rdfs-krule.rdf.

Paul

On Sep 18, 2007, at 10:40 AM, Schmitz, Jeffrey A wrote:

> Hello,
>    I'm trying to get my arms around how to return inferenced results
> from Mulgara.  I'm using the CameraPhone.owl ontology, but I can only
> get asserted results returned from queries.  The query I'm doing is:
>
> select $s <rdfs:subclassof> $o from
> <rmi://B894586.mw.nos.boeing.com/server1#cameraphone> where
> $s <rdfs:subClassOf> $o;
>
> I would expect results such as:
>
> CameraPhone rdfs:subclassof PurchaseableItem
>
> To be returned, but it is not.  Am I possibly missing a step  
> somewhere?
> Or do my queries need to add all the inferencing logic within it
> (hopefully not)?
>
> I did all the steps specified here:
>
> http://docs.mulgara.org/inferencing/inferexample.html
>
> One thing to note is I'm behind a firewall, so my server won't have
> access to the rdfs and owl schema's using their internet addresses.
> Will I have to load them locally and tell mulgara to use the local
> copies?  If so, how do you do that?
>
> Thanks,
> Jeff
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