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From Hasan Hasan <ha...@trialox.org>
Subject Re: [jira] [Commented] (CLEREZZA-761) Implement SPARQL PreParser to support fastlane
Date Tue, 02 Apr 2013 20:45:17 GMT
Hi Reto,

after studying carefully the description and examples in
http://www.w3.org/TR/sparql11-query/#rdfDataset
I think the PreParser should - as you suggested - have a TcProvider to
return all TripleCollections, in case no FROM NAMED clause is specified in
the query.

How should we pass the TcProvider to the PreParser? In a separate method,
e.g.,

public void setTcProvider(TcProvider tcProvider);

Default TcProvider would be TcManager.

Cheers
Hasan



On Tue, Apr 2, 2013 at 12:34 PM, Reto Bachmann-Gmür <reto@apache.org> wrote:

> Hi,
>
> The query SELECT DISTINCT ?g { GRAPH ?g { ?s ?p ?o } } can obviously only
> be answered correctly by a sparql engine that knows about all the available
> graphs. As typically not all graphs are provided by the same provider this
> means the query has to be slow laned.
>
> If the pre parser returns only the default graph as this is currently the
> case:
>
> zz>spp.getReferredGraphs("SELECT DISTINCT ?g { GRAPH ?g { ?s ?p ?o } }",new
> UriRef("urn:x-localinstance:/content.graph"))
> res0: java.util.Set[org.apache.clerezza.rdf.core.UriRef] =
> [<urn:x-localinstance:/content.graph>]
>
> The query would be fastlaned to the TcProvider providing the Graph
> <urn:x-localinstance:/content.graph> which potentially knows about none of
> the other graphs.
>
> So I think either the preparser has the TcManager and returns all the
> TripleCollections or it returns a special value to tell the caller that the
> set of affected graphs cannot be limited (return null).
>
> Currently clerezza correctly returns all triple collections:
>
> zz>val q = qp.parse("SELECT DISTINCT ?g { GRAPH ?g { ?s ?p ?o } }")
> q: org.apache.clerezza.rdf.core.sparql.query.Query =
> SELECT DISTINCT
> ?g
> WHERE
> { GRAPH ?g { ?s ?p ?o .
> } }
> zz>val r = tcm.executeSparqlQuery(q.asInstanceOf[SelectQuery], new
> SimpleMGraph)
> r: org.apache.clerezza.rdf.core.sparql.ResultSet =
> org.apache.clerezza.rdf.jena.sparql.ResultSetWrapper@b0d2ffd
> zz>r.next
> res5: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/tbox.graph>}
> zz>r.next
> res6: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/config.graph>}
> zz>r.next
> res7: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/content.graph>}
> zz>r.next
> res8: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/documentation.graph>}
> zz>r.next
> res9: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/web-resources-cache.graph1364897492157>}
> zz>r.next
> res10: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/graph-access.graph>}
> zz>r.next
> res11: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/web-resources.graph>}
> zz>r.next
> res12: org.apache.clerezza.rdf.core.sparql.SolutionMapping =
> {org.apache.clerezza.rdf.core.sparql.query.Variable@67
> =<urn:x-localinstance:/system.grap
>
> Cheers,
> Reto
>
> On Tue, Apr 2, 2013 at 8:10 AM, Hasan Hasan <hasan@trialox.org> wrote:
>
> > Hi Reto, all
> >
> > Two issues here:
> >
> > First the query: SELECT DISTINCT ?g { GRAPH ?g { ?s ?p ?o } }
> > does not specify NAMED graphs.
> > If the query is as follows
> > SELECT DISTINCT ?g FROM NAMED http://example.org/g1 { GRAPH ?g { ?s ?p
> ?o
> > }
> > }
> > then the engine will return http://example.org/g1
> > because the clause GRAPH refers only NAMED graphs as mentioned by Andy
> >
> > Second the parser: I think the parser needs not know about TcManager or
> > other providers in this case, because
> > the named graphs are all specified in the query.
> >
> > Cheers
> > Hasan
> >
> >
> >
> > On Fri, Mar 29, 2013 at 1:47 PM, Reto Bachmann-Gmür (JIRA)
> > <jira@apache.org>wrote:
> >
> > >
> > >     [
> > >
> >
> https://issues.apache.org/jira/browse/CLEREZZA-761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13617295#comment-13617295
> > ]
> > >
> > > Reto Bachmann-Gmür commented on CLEREZZA-761:
> > > ---------------------------------------------
> > >
> > > zz>import org.apache.clerezza.rdf.core.sparql._
> > > import org.apache.clerezza.rdf.core.sparql._
> > > zz>val spp = $[SparqlPreParser]
> > > spp: org.apache.clerezza.rdf.core.sparql.SparqlPreParser =
> > > org.apache.clerezza.rdf.core.sparql.SparqlPreParser@3aa78e7a
> > > zz>spp.getReferredGraphs("SELECT DISTINCT ?g { GRAPH ?g { ?s ?p ?o }
> }",
> > > new UriRef("urn:x-localinstance:/content.graph"))
> > > res0: java.util.Set[org.apache.clerezza.rdf.core.UriRef] =
> > > [<urn:x-localinstance:/content.graph>]
> > > zz>
> > >
> > > As discussed in
> > >
> >
> http://mail-archives.apache.org/mod_mbox/clerezza-dev/201303.mbox/%3C51498242.4020809@apache.org%3Ethisshouldreturn
all the graphs in the dataset. I think that
> > > SParqlPreParser being a service it could consider by default TcManager
> > > being the dataset, but it probably should also have a method that takes
> > any
> > > TcProvider as dataset and return it's triple collections.
> > >
> > > > Implement SPARQL PreParser to support fastlane
> > > > ----------------------------------------------
> > > >
> > > >                 Key: CLEREZZA-761
> > > >                 URL:
> > https://issues.apache.org/jira/browse/CLEREZZA-761
> > > >             Project: Clerezza
> > > >          Issue Type: New Feature
> > > >            Reporter: Hasan
> > > >            Assignee: Hasan
> > > >
> > > > The purpose is to have a class with a method to obtain referred
> graphs
> > > in a SPARQL Query or SPARQL Update
> > >
> > > --
> > > This message is automatically generated by JIRA.
> > > If you think it was sent incorrectly, please contact your JIRA
> > > administrators
> > > For more information on JIRA, see:
> > http://www.atlassian.com/software/jira
> > >
> >
>

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