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Re: Action 369 -- Look at property path tests

From: Gregory Williams <greg@evilfunhouse.com>
Date: Tue, 25 Jan 2011 11:16:28 -0500
Cc: W3C SPARQL Working Group <public-rdf-dawg@w3.org>
Message-Id: <EC2BAA9D-2E5A-481D-9317-A1C8E99F2629@evilfunhouse.com>
To: Matthew Perry <matthew.perry@oracle.com>
On Jan 25, 2011, at 9:41 AM, Matthew Perry wrote:

> I have reviewed the property path tests. We need tests for {m,n}, {,n}, ? and () for precedence, and I think we need more tests for combinations of property path constructs.
> I have disagreements with some of the answers given in the current tests.
> 1) pp15 -- I don't see why we are returning results on an empty dataset.

pp15 returns results because zero-length property paths bind the path endpoints to any subjects or objects in the graph *and* any bound term explicitly in the query. So in pp15, ?X :p{0} "o" will bind ?X="o". Likewise for ?Y and ?Z. This is part of the evaluation semantics for ZeroLengthPath (http://www.w3.org/2009/sparql/docs/query-1.1/rq25.xml#sparqlAlgebraEval), though maybe it could be made clearer in the description of property paths in section 9 (from the evaluation semantics, I take "graph node" in section 9 to include terms not necessarily in the dataset but that are present in the query).

Received on Tuesday, 25 January 2011 16:16:58 UTC

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