[Mulgara-general] SPARQL filter not being applied.

[Jim Irwin]

> Date: Mon, 22 Jun 2009 14:38:52 -0700                               
> From: Paul Gearon <gearon at ieee.org>                                 
> Subject: Re: [Mulgara-general] SPARQL filter not being applied.     
> To: Mulgara General <mulgara-general at mulgara.org>                   
>
>  (snip)
> When the filters are reversed I was expecting it to filter by the   
> ?rvxtmp_1 variable equaling "Gesture", and NOT by the ?instance     
> variable being blank (meaning that only the second filter was being
> applied). Is that what happened? Perhaps your data is set up so that
> the domain of rbrnr:Object-Name is not likely to be blank? (meaning
> that your data is shaped such that this condition is inherent and   
> needn't be filtered on)                                             

Yes, that is what happened -- it filtered on ?rvxtmp_1 variable equaling 
"Gesture".  There were no cases where ?instance was blank, so I could 
not confirm that only the second filter is being applied.   The filters 
are automatically generated by our query processing code, so it is not 
easy to convert them to &&, nor do we know ahead of time whether the 
isBLANK test is necessary or not, so it is always automatically added.

I suppose we could always wrap the str() function around any variable 
which is compared to an untyped, non-numeric literal in our query 
builder.  It is a bit too much to expect our users to understand the 
nuances of xsd:strings versus plain literals, and they certainly expect 
to find "x"^^xsd:string if they search for "x" -- this was precisely the 
complaint we received from the user who expected to see at least one 
known result when he searched for "Gesture".   I also doubt that our 
users would object if we returned other datatypes having the same 
lexical form, so doing more than inserting a str() function is probably 
not necessary.

Jim