[
https://issues.apache.org/jira/browse/JENA-1945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17187063#comment-17187063
]
Claus Stadler commented on JENA-1945:
-------------------------------------
Hi Andy,
I see that w.r.t. property paths the whole concept breaks because with SPARQL
1.1 the needed rewrite can no longer be expressed and I agree that under this
consideration Algebra.unionDefaultGraph should be deprecated.
Then again, having some transformation that makes a SPARQL query written for an
RDF graph (i.e. just using triple patterns) run on all named graphs (at least
on a best effort basis) *independently from the RDF DBMS* is still a very
useful one. E.g. for RDF stream processing one typically wraps each event in a
named graph. The question would be whether and where it would fit in Jena.
Btw, AFAIK there is no unionDefaultGraph-like flag in the SPARQL protocol
itself or is there?
> Algebra.unionDefaultGraph: OpPath not handled
> ---------------------------------------------
>
> Key: JENA-1945
> URL: https://issues.apache.org/jira/browse/JENA-1945
> Project: Apache Jena
> Issue Type: Improvement
> Components: ARQ
> Affects Versions: Jena 3.16.0
> Reporter: Claus Stadler
> Priority: Major
>
>
> {code:java}
> System.out.println(
> Algebra.unionDefaultGraph(
> Algebra.compile(
> QueryFactory.create("SELECT * { ?s <urn:p> ?o }"))));
> /* Yields correct result:
> (distinct
> (graph ??_
> (bgp (triple ?s <urn:p> ?o))))
> */
> System.out.println(
> Algebra.unionDefaultGraph(
> Algebra.compile(
> QueryFactory.create("SELECT * { ?s <urn:p1>/<urn:p2>/<urn:p3> ?o }"))));
> /* Yields incorrect result because wrapping with graph ??_ (and distinct) is
> missing:
> (path ?s (seq (seq <urn:p1> <urn:p2>) <urn:p3>) ?o)
> */
> {code}
>
> It seems
> [TransformUnionQuery.java|https://github.com/apache/jena/blob/master/jena-arq/src/main/java/org/apache/jena/sparql/algebra/TransformUnionQuery.java#L34]
> lacks the handling of (at least) OpPath
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
