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Re: XML literals poll

From: Charles Greer <cgreer@marklogic.com>
Date: Mon, 21 Nov 2011 12:16:29 -0800
Message-ID: <4ECAB19D.5080509@marklogic.com>
To: Richard Cyganiak <richard@cyganiak.de>
CC: RDF Working Group WG <public-rdf-wg@w3.org>
On 11/21/2011 11:32 AM, Richard Cyganiak wrote:
> Below are six questions on XML literals. Please help the WG get a feeling for the general opinion within the group by answering the questions. Answers in the usual +1/±0/-1 style are appropriate.
>
> Thanks,
> Richard
>
>
>
> Q1. Should the specs define a way to compare XML literals based on value?
>
> In other words, in the same way that integers 7 and 007 have the same value, should<foo/>  and<foo></foo>  be defined as having the same value?
-1.  Hopefully this work will push XML comparison outside of the realm 
of RDF specification.
>
>
> Q2. Should the specs say that RDF implementations MUST support value-based comparison?
>
> In other words, assuming the specs define a value space that answers Q1 in the affirmative, is it required that all RDF toolkits implement some sort of canonicalization somewhere in the process?
>
-1 for XMLLiteral.  I'd support having value-as-string comparison, 
because string equality does entail XML equality.  I don't know whether 
or not that's a useful or actionable distinction.
>
> Q3. Should the *lexical* space be in canonical form?
>
> In other words, should
>    <>  ex:value "<foo/>"^^rdf:XMLLiteral.
>    <>  ex:value "<foo></foo>"^^rdf:XMLLiteral.
>
> result in a graph with one triple (canonicalize) or two (don't canonicalize)? Note that if you answer “two”, then it is unavoidable that round-tripping an XML literal, or storing the same XML literal in two different formats (say, RDF/XML and Turtle) and reading it again, will sometimes result in a different triple (with the same value though).
-1
>
>
> Q4. Should *invalid XML* be allowed in the lexical space?
>
> In other words, should "</bar !!!>"^^rdf:XMLLiteral be ill-typed (just like "AAA"^^xsd:integer) or well-typed (just like"</bar !!!>"^^xsd:string)?
>
  I think you're asking about well-formedness.  XMLLiteral should be 
well-formed.
>
> Q5. Should the specs say that RDF/XML parsers MUST canonicalize when handling parseType="literal"?
>
> RDF/XML parsers are often implemented on top of an XML parser, and hence they don't have access to a low-level representation of the XML literal, e.g., did it use single or double quotes in the attributes, what order where the attributes in, or how many spaces were between them? If they don't canonicalize, then two different RDF/XML parsers would be pretty much guaranteed to parse the same RDF/XML file into different triples (or even different runs of the same parser over the same file could yield different triples).
>
I don't know, probably.  RDF/XML after all is an RDF serialization 
format, not an XML dialect. I'd hope that we could round-trip to RDF/XML 
somehow.    +0.5
>
> Q6. Should it be required that producers of XML literals in concrete syntaxes (Turtle, N-Triples, other parseTypes in RDF/XML) canonicalize the literals themselves?
>
> If the lexical space is canonicalized (see Q3), then it means that canonicalization either has to be done by parsers (see Q5), or by content producers.
>
-1.  I don't think that XMLLiterals will very often be RDF/XML.
>
> (FWIW, the RDF 2004 design is: Q1: Yes. Q2: Yes. Q3: Yes. Q4: No. Q5: Yes. Q6: Yes.)


-- 
Charles Greer
Senior Engineer
MarkLogic Corporation
charles.greer@marklogic.com
Phone: +1 707 408 3277
www.marklogic.com

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Received on Monday, 21 November 2011 20:17:04 GMT

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