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Re: Publish RDF Concepts as revised WD? (was: Re: Agenda 16 May telecon)

From: Richard Cyganiak <richard@cyganiak.de>
Date: Fri, 18 May 2012 12:44:15 +0100
Cc: Ivan Herman <ivan@w3.org>, Guus Schreiber <guus.schreiber@vu.nl>, RDF WG <public-rdf-wg@w3.org>
Message-Id: <233F8786-81DC-4D70-AE99-122F4421EB35@cyganiak.de>
To: Steve Harris <steve.harris@garlik.com>
On 18 May 2012, at 12:16, Steve Harris wrote:
>>>> I have hit a problem today, when implementing the HTML literal in my RDFa distiller software. The problem is that the underlying library does not give me a method whereby I can take the original file's element content from its corresponding DOM node and dump it into a string (that can be used for the RDF Literal). (Technically, the library does not implement the innerHTML attribute on the DOM Element Node.) I can only take the content and dump it into a string in full XML syntax.
>>>> 
>>>> So, for example, if I have, in HTML5+RDFa:
>>>> 
>>>> <div property="ex:something" datatype="rdf:HTML"><p>Inner</div>
>>>> 
>>>> then the only way I can generate an HTML Literal is 
>>>> 
>>>> <> ex:something "<p>Inner</p>"^^rdf:HTML .
>>>> 
>>>> Another library used by another tool may have the necessary method. For the same RDFa fragment it can generate:
>>>> 
>>>> <> ex:something "<p>Inner"^^rdf:HTML .
>>>> 
>>>> With the current definition of the HTML Literal both RDFa tools are correct and compliant: the HTML Literals, though lexically different, are identical in terms of the generated DOM, based on the HTML5 specification. Ie, if a triple store implements the identity in the value space, there would be no duplication of triples if both tools dump their content into the same space. If only lexical identity is available then... it becomes messy.
>>> 
>>> Sure, but what usecase do you have for being able to want to compare these - even though though lexically different - semantically?
>> 
>> Test suites for HTML5+RDFa parsers.
> 
> Surely there you'd "just" need a graph isomorphism test?

No, implementing an HTML5+RDFa parser that produces an isomorphic graph is often impossible, as Ivan explained in the text quoted above.

> You don't care if the input documents are semantically equivalent?

A test suite for HTML5+RDFa parsers would likely say that a conforming parser MUST generate an RDF graph that is isomorphic to the test case graph, except that literals MAY be replaced by other literals of equal value.

(In a perfect world, RDF Semantics would define something like LV-Entailment (literal value entailment) that captures this notion. So one could say that an HTML5+RDFa parser MUST generate a graph that is LV-equivalent to the test case graph.)

Best,
Richard



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Received on Friday, 18 May 2012 11:44:50 GMT

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