RE: [Myexperiment-discuss] MyExperiment SPARQL endpoint returns incorrect results

[David R Newman]

Hi Peter,

I have been waiting on a colleague of mine to finish his reasoner for 4Store 
[1] before upgrading.  He is currently upgrading the reasoner so it supports 
Raptor2 (latest versions of 4Store only support Raptor2 rather than Raptor).  
Although upgrading doesn't take that long, all being well, I like to make sure 
any version upgrades I do work on a test server before deploying them on the 
live server.  For that reason, version upgrades can be a bit sporadic, 
dependent on me finding time out from the project I am employed on.  If this is 
a critical feature you require, I will see if I can set aside some time to look 
into doing an upgrade.  When I do, I will probably upgrade to a checkout from 
GIT, as I am aware of some significant performance improvements added since 
1.1.2.

Regards

David Newman

[1] http://4sreasoner.ecs.soton.ac.uk/

-----Original Message-----
From: address@hidden [mailto:address@hidden On Behalf Of Peter Ansell
Sent: 22 March 2011 02:33
To: address@hidden
Subject: [Myexperiment-discuss] MyExperiment SPARQL endpoint returns incorrect 
results

Hi,

The SPARQL endpoint at http://rdf.myexperiment.org/sparql isn'
working properly right now for queries with optional unbound items.

The query below should only return bindings for ?linkedRecordType
?label, ?title, or ?skoslabel when they actually exist.

CONSTRUCT {
?s ?p <http://www.myexperiment.org/workflows/72> .
?s a  ?linkedRecordType .
?s  <http://www.w3.org/2000/01/rdf-schema#label> ?label .
?s  <http://purl.org/dc/elements/1.1/title> ?title .
?s  <http://www.w3.org/2004/02/skos/core#prefLabel> ?skoslabel .
} WHERE {
?s ?p <http://www.myexperiment.org/workflows/72> .
OPTIONAL { ?s a ?linkedRecordType . }
OPTIONAL { ?s  <http://www.w3.org/2000/01/rdf-schema#label> ?label . }
OPTIONAL { ?s <http://purl.org/dc/elements/1.1/title> ?title . }
OPTIONAL { ?s <http://www.w3.org/2004/02/skos/core#prefLabel> ?skoslabel . }
} LIMIT 500 OFFSET 0

Right now the Garlik 4Store SPARQL engine is returning bindings that
don't actually exist as blank nodes with an rdf:nodeID="LL". This is
worse than it seems as it is inconsistent. It implies that all of the
resources that will be bound to ?s have labels/titles/prefLabel's, and
that they all point to the same blank node, although there is no other
information available about the blank node they reference.

You may want to try upgrading to the latest version of 4Store as you
are one version behind right now, 1.1.2 is the latest [1].

Cheers,

Peter

[1] http://4store.org/download/

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