W3C home > Mailing lists > Public > public-rdb2rdf-comments@w3.org > September 2013

add NULL cases to conformance test

From: Vladimir Alexiev <vladimir.alexiev@ontotext.com>
Date: Tue, 17 Sep 2013 23:03:20 +0300
To: <public-rdb2rdf-comments@w3.org>
Cc: "'Gregg Garcia'" <GGarcia@getty.edu>
Message-ID: <00c801ceb3e0$f5de8410$e19b8c30$@alexiev@ontotext.com>
Hi everyone!

If a column value (or any of the columns in a rr:template) is null, an r2rml processor should skip the involved triple.
If the rr:subjectMap column is null, it should skip all triples in that rr:TriplesMap.
This is especially important since R2RML doesn't offer any conditionals.

This behaviour is stated quite definitely at:
http://www.w3.org/2001/sw/rdb2rdf/wiki/RDBNullValues#R2RML

1. But IMHO the R2RML spec is silent on what happens when a subjectMap or objectMap is null. If we read pedantically: 
"A predicate-object map is a function that creates *one* or more predicate-object pairs for each logical table row" 
then it should generate a triple with null.

Please add some langauge to the effect of the above wiki page.

2. Please also add conformance tests with NULLs.
E.g. the perl module RDF::RDB2RDF does NOT ignore nulls, even though it's passed the conformance test.

Thanks!
--
Vladimir Alexiev, PhD, PMP
Lead, Data and Ontology Management Group
Ontotext Corp, www.ontotext.com
Sirma Group Holding, www.sirma.com
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Received on Tuesday, 17 September 2013 20:03:49 UTC

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