For some reason, I'm having trouble executing the "sub-query" sparql
query using the SPIN api. Even after simplifying the query to remove
the LET and the SPIN function, the query with sub-queries doesn't return
results when it should.
Specifically, when I execute the following query in my code using the
SPIN API, as well as when I execute it from the TBC SPARQL tab, it works
correctly:
SELECT ?value
WHERE {?user a ModelManagement:User .
?user ModelManagement:firstName ?value
}
However, when I execute the following, I think logically equivalent
query, I get no results:
SELECT ?value
{
{SELECT ?user
WHERE {
?user a ModelManagement:User .
}
}
{SELECT ?user ?value
WHERE {
?user ModelManagement:firstName ?value
}
}
}
This query does work correctly from the TBC SPARQL tab, and I can also
run this query in my code using just the jena/arq API and it works
correctly.
I've pasted below the code I use to execute the queries using the SPIN
API, which seems to work for most cases. I have a feeling there's a
more concise way to do this, but that's a topic for another post...
//Create the ARQ Query from the SPARQL string.
arqQuery = QueryFactory.create(sparqlStr,
Syntax.syntaxARQ);
//Get the ARQ2SPIN utility, specifying model to be
queried.
ARQ2SPIN a2s = new
ARQ2SPIN(modelManagementInst.memModel);
//Create a SPIN query from the ARQ Query
org.topbraid.spin.model.Query spinQuery =
a2s.createQuery(arqQuery,
null);
//Wrap up both queries in a SPIN wrapper.
QueryWrapper wrapper = null;
String ruleText = null;
if (spinQuery != null) {
StringPrintContext p = new StringPrintContext();
spinQuery.print(p);
if (ruleText == null) {
ruleText = p.getString();
}
arqQuery =
ARQFactory.get().createQuery(modelManagementInst.memModel,
p.getStringBuilder().toString());
wrapper = new QueryWrapper(arqQuery, ruleText,
spinQuery,
ruleText);
}
//Get the arq query from the wrapper
arqQuery = wrapper.getQuery();
//Get the query execution
QueryExecution selQe =
ARQFactory.get().createQueryExecution(
arqQuery,
modelManagementInst.memModel);
//Execute it
ResultSet rs = selQe.execSelect();
> -----Original Message-----
> From: Schmitz, Jeffrey A
> Sent: Thursday, May 28, 2009 11:06 AM
> To: [email protected]
> Subject: [tbc-users] Re: [SPIN] Using FILTER with function arguments
>
>
> No, that's not working in this case...
>
> SELECT ?user ?value
> WHERE {
> LET(?user := :getProjectUser("DEFAULT_PROJECT", "xxx"))
> FILTER (bound(?user)) ?user :firstName ?value }
>
> Still returns everything with a firstName property.
>
> > -----Original Message-----
> > From: Holger Knublauch [mailto:[email protected]]
> > Sent: Thursday, May 28, 2009 10:22 AM
> > To: [email protected]
> > Subject: [tbc-users] Re: [SPIN] Using FILTER with function arguments
> >
> >
> > Jeff,
> >
> > wouldn't it be sufficient to add a FILTER bound(?var) after the
> > function call?
> >
> > Holger
> >
> >
> > On May 28, 2009, at 7:06 AM, Schmitz, Jeffrey A wrote:
> >
> > >
> > > "The function returns no binding and therefore ?user is
> unbound and
> > > will be iterating over all possible subjects of the firstName
> > > triples."
> > >
> > > Hmmm, not what I was expecting. I guess I would have
> > expected it to
> > > act more like normal SPARQL variable chaining occurrs,
> e.g. in the
> > > following
> > > query:
> > >
> > > SELECT ?user ?value
> > > WHERE {?user a :NonExistantClass .
> > > ?user :firstName ?value}
> > >
> > > ?user is "unbound" after the first line (NonExistantClass doesn't
> > > really exist), and this query returns no results instead of
> > everything
> > > in the model with a firstName property. Even if you reverse the
> > > order:
> > >
> > > SELECT ?user ?value
> > > WHERE {?user :firstName ?value .
> > > ?user a :NonExistantClass .
> > > }
> > >
> > > You still get no results. But change it to something like:
> > >
> > > SELECT ?user ?value
> > > WHERE {(LET ?user := :filterOnClass(:NonExistantClass)
> > > ?user :firstName ?value}
> > >
> > > And you do get everything in the model with a firstName property.
> > >
> > > Be that as it may, using subqueries I think I'm able to get the
> > > behavior I'm looking for. A little verbose, but if I understand
> > > things, I think you'd have to do this anytime you wanted to use a
> > > re-usable SPIN filtering function:
> > >
> > >
> > > SELECT ?user ?value
> > > {
> > > {SELECT ?user
> > > WHERE {
> > > LET(?user :=
> > > ModelManagement:getProjectUser("DEFAULT_PROJECT",
> > > "xxx"))
> > > }
> > > }
> > > {SELECT ?user ?value
> > > WHERE {
> > > ?user ModelManagement:firstName ?value
> > > }
> > > }
> > > }
> > >
> > > In the above query, if the user specified in the LET
> (xxx) doesn't
> > > exist, nothing is returned.
> > >
> > >
> > >> -----Original Message-----
> > >> From: Holger Knublauch [mailto:[email protected]]
> > >> Sent: Wednesday, May 27, 2009 9:38 PM
> > >> To: [email protected]
> > >> Subject: [tbc-users] Re: [SPIN] Using FILTER with function
> > arguments
> > >>
> > >>
> > >>
> > >> On May 27, 2009, at 12:21 PM, Schmitz, Jeffrey A wrote:
> > >>
> > >>>
> > >>> It's getting curiousor and curiousor...
> > >>>
> > >>> Using the TBC SPARQL tab, when I call a function that filters
> > >>> according to an argument, e.g.:
> > >>>
> > >>> SELECT ?user
> > >>> WHERE {
> > >>> ?project ModelManagement:hasUser ?user .
> > >>> ?user Common:name ?username .
> > >>> FILTER (?username = ?arg1) .
> > >>> }
> > >>
> > >> If the function returns no binding then it will be
> comparable to a
> > >> wildcard in the query below.
> > >>
> > >>>
> > >>>
> > >>> As long as I pass in an argument that has a match:
> > >>>
> > >>> SELECT ?value
> > >>> WHERE {LET(?user := ModelManagement:getProjectUser("john"))
> > >>> ?user ModelManagement:firstName ?value}
> > >>>
> > >>> the function returns just one result as expected (in this
> > case for
> > >>> some reason the blank result rows aren't returned).
> > However, if I
> > >>> pass in a value that has NO matches:
> > >>>
> > >>> SELECT ?value
> > >>> WHERE {LET(?user := ModelManagement:getProjectUser("xxx"))
> > >>> ?user ModelManagement:firstName ?value}
> > >>>
> > >>>
> > >>> It acts like the FILTER statement isn't there, and all
> > >> User's names in
> > >>> the model are returned. I would have expected no results to be
> > >>> returned. Btw, I'm seeing this same behavior in my code
> > too. Am I
> > >>> thinking about this wrong, or is there perhaps a
> problem with how
> > >>> FILTER works within a Function?
> > >>
> > >> No, the behavior is correct (as far as I understand your
> example).
> > >> The function returns no binding and therefore ?user is
> unbound and
> > >> will be iterating over all possible subjects of the firstName
> > >> triples.
> > >>
> > >> In your first email, please keep in mind that the
> > execution order of
> > >> ARQ might be different from what you have typed it. In
> > particular, I
> > >> find often that LET statements are executed at the end,
> > and therefore
> > >> lead to more iterations than expected.
> > >>
> > >> Holger
> > >>
> > >>
> > >>>
> > >>
> > >
> > > >
> >
> >
> > >
> >
>
> >
>
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