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Exclusive Canonicalization of XMLLiterals in SPARQL

From: Manu Sporny <msporny@digitalbazaar.com>
Date: Tue, 20 Oct 2009 23:08:15 -0400
Message-ID: <4ADE7B1F.5000706@digitalbazaar.com>
To: "Seaborne, Andy" <andy.seaborne@hp.com>
Hi Andy, (bcc: RDFa mailing list)

I have an action in the RDFa Task Force to contact you and discuss
Exclusive Canonicalization of XML Literals when RDF/XML is given as
input to a SPARQL processor.

We have had a number of people assert that RDFa Processors should always
generate Exclusive Canonical XML Literals. Ivan Herman asserted that
Exclusive Canonicalization should be performed on RDF/XML input when it
is de-serialized into an RDF graph (before the SPARQL query runs on the

The RDFa Test Suite SPARQL queries were updated to test for Exclusive
Canonical XMLLiterals (in the tests that contain XMLLiterals) and it has
been shown that Exclusive Canonicalization is not occurring in the
SPARQL service provided at SPARQL.org.

Specifically, some of the RDFa processors are generating RDF/XML which
contain XML Literals. Those XML Literals are not canonicalized in their
RDF/XML form. The RDF/XML is sent to SPARQL.org. The RDFa processors
that perform canonicalization before serializing to RDF/XML pass the XML
Literal tests. The RDFa processors that do not perform canonicalization
before serializing to RDF/XML do not pass the XML Literal tests.

Here is a pointer to the start of the thread:


Do you think that RDF/XML should be canonicalized when being
de-serialized into the graph on which the SPARQL query operates?

If so, is there a bug in SPARQL.org that is causing the RDF/XML to not
be canonicalized and is thus causing the SPARQL queries to fail?

-- manu

Manu Sporny (skype: msporny, twitter: manusporny)
President/CEO - Digital Bazaar, Inc.
blog: Establishing an Open Digital Media Commerce Standard
Received on Wednesday, 21 October 2009 03:08:46 UTC

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