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Re: XML literals poll

From: Peter Frederick Patel-Schneider <pfps@research.bell-labs.com>
Date: Mon, 21 Nov 2011 14:43:19 -0500
Message-ID: <20111121.144319.2204205505882644550.pfps@research.bell-labs.com>
To: <richard@cyganiak.de>
CC: <public-rdf-wg@w3.org>
From: Richard Cyganiak <richard@cyganiak.de>
Subject: XML literals poll
Date: Mon, 21 Nov 2011 13:32:01 -0600

> 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? 

This is inherent in being a datatype, so +1

> 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? 

What is an RDF implementation?

> 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). 


> 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)? 


> 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). 


> 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. 

Received on Monday, 21 November 2011 19:45:11 UTC

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