Spaces inserted by PropertyPathBuilder cause problems with AllegroGraph

[reckart]

Current Behavior

When building a property path using PropertyPathBuilder, the path contains spaces, e.g. after operators such as +. It appears that AllegroGraph does not like that.

Looking in the SPARQL specs, it seems that there should not be spaces before postfix operators (like '+') or after prefix operators ('^').

AllegroGraph is the only SPARQL backend I have seen so far that seems to be picky on this issue.

Expected Behavior

PropertyPathBuilder should generate standards-compliant property paths.

Steps To Reproduce

Ok, this is tricky - you'd need an AllegroGraph instance to actually reproduce it. But I'll give you examples.

This query constructed using the RDF4J API fails:

Query   : 
          SELECT DISTINCT ?subj
          FROM <http://testgraph>
          WHERE { { { ?subj <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> + <http://example.org/#property-1> .
          FILTER EXISTS { { ?subj <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> . } UNION { ?subj <http://www.w3.org/2000/01/rdf-schema#subClassOf> + <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> . } UNION { [] <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> ?subj . } UNION { ?subj <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> [] . } } } } }
          LIMIT 200

----
org.eclipse.rdf4j.query.QueryEvaluationException: Line 3, Found !<HTTP://EXAMPLE.ORG/#PROPERTY-1> (of type q_iri_ref). Was expecting one of: DECIMAL-POSITIVE, DOUBLE-POSITIVE, INTEGER-POSITIVE. while running query:
SELECT DISTINCT ?subj
FROM <http://testgraph>
WHERE { { { ?subj <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> + <http://example.org/#property-1> .
FILTER EXISTS { { ?subj <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> . } UNION { ?subj <http://www.w3.org/2000/01/rdf-schema#subClassOf> + <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> . } UNION { [] <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> ?subj . } UNION { ?subj <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> [] . } } } } }
LIMIT 200

This query works after I have adjusted classes such as org.eclipse.rdf4j.sparqlbuilder.constraint.propertypath.OneOrMorePath to not add a space:

Query   : 
          SELECT DISTINCT ?subj
          FROM <http://testgraph>
          WHERE { { { ?subj <http://www.w3.org/2000/01/rdf-schema#subPropertyOf>+ <http://example.org/#property-1> .
          FILTER EXISTS { { ?subj <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> . } UNION { ?subj <http://www.w3.org/2000/01/rdf-schema#subClassOf>+ <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> . } UNION { [] <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> ?subj . } UNION { ?subj <http://www.w3.org/2000/01/rdf-schema#subPropertyOf> [] . } } } } }
          LIMIT 200
Results : 2 in 520ms
          KBHandle[identifier=http://example.org/#subproperty-1-1,name=<null>]
          KBHandle[identifier=http://example.org/#subproperty-1-1-1,name=<null>]

Version

4.3.9

Are you interested in contributing a solution yourself?

Perhaps?

Anything else?

I can provide a PR to remove the spaces, but I'd prefer not having to produce a full unit test for this as this would involve booting up an AllegroGraph, filling it with data and testing queries against it.

Tested against Docker image franzinc/agraph:latest (ID sha256:5c3cf4887ecf832a68fb94360edfae57cf3506d3604864967266362f8a733189)

[tpluscode]

FYI, I reported this to AllegroGraph this week. Will be fixed in version 8.1.1