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RE: Comments on RDF/A draft

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Fri, 29 Oct 2004 09:17:49 +0100
To: "'Ralph R. Swick'" <swick@w3.org>
Cc: <public-rdf-in-xhtml-tf@w3.org>, "'Steven Pemberton'" <steven@w3.org>
Message-ID: <005f01c4bd8f$cab0e4a0$0e01a8c0@W100>

Hi Ralph,

Thanks for your extremely useful comments.

Just to clarify the motivation for the RDF/A document; we felt that
discussing the new metadata features in XHTML 2 within the context of XHTML
2 was a little restrictive. We decided to take everything out into a
separate document so that we could talk with you 'RDF guys' more easily
about the RDF-ness of the proposal. Once all the comments were in, we
planned to modify RDF/A to take them into account, and only then work
everything back into the original two chapters in XHTML 2.

Of course, we also hope that making it a separate module will allow it to be
used in other situations -- one of my favourite examples is marking up the
source of a quote when the quote is in both XHTML and SVG -- but the main
motivation was as a tool with which to talk to you RDF experts. And with the
excellent comments from Jeremy, yourself and others, we feel it has
definitely worked well and consequently we're now in a pretty good position
to pop back up the stack.

Best regards,


Mark Birbeck
x-port.net Ltd.

e: Mark.Birbeck@x-port.net
t: +44 (0) 20 7689 9232
w: http://www.formsPlayer.com/

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> -----Original Message-----
> From: Ralph R. Swick [mailto:swick@w3.org] 
> Sent: 29 October 2004 04:58
> To: Mark Birbeck; Steven Pemberton
> Cc: public-rdf-in-xhtml-tf@w3.org
> Subject: Comments on RDF/A draft
> Mark and Steven;
> Very nice work on the RDF/A proposal [1].  You have made a 
> major step forward to providing a way to tie RDF semantics 
> into XHTML documents. I applaud your efforts to produce a 
> module that is potentially usable with other XML languages as 
> well as XHTML.  I do hope that in the process of modularizing 
> this you will not make it more cumbersome for users of this 
> module than the meta information module in the 22 July XHTML 
> 2.0 working draft.
> [1] http://www.formsplayer.com/notes/rdf-a.html
>     Last Modified: 2004-09-22
> This RDF/A draft certainly addresses my main concern with the 
> 22 July XHTML 2.0 working draft; this document clearly and as 
> nearly as I can tell with a moderatly thoughtful 
> read-through, unambiguously connects the semantics of these 
> proposed attributes to RDF concepts. Now I have one comment 
> in the opposite direction; you've gone so far towards 
> creating a module that could be acceptable to many XML 
> document types that you've forgotten to give the original -- 
> and dare I say -- primary motivation; to permit precise RDF 
> semantics to be carried within XHTML documents.  I suggest 
> that the Abstract specifically cite XHTML as one of the 
> target XML document types.
> I didn't find any specification of the namespace within which 
> you expect these new attributes and the hasReferenceTo 
> property to be found.  That really makes this draft 
> incomplete.  I hope that they will at least be part of the 
> http://www.w3.org/2002/06/xhtml2 namespace (as your examples 
> seem to suggest).
> The bulk of my comments on this draft are editorial.
> Section 1 Motivation: "... the syntax of RDF/XML is too 
> unwieldy for use as a mechanism for adding metadata to a 
> document about the document itself."  This is a value 
> judgement with which reasonable people can disagree.  
> Certainly there are instances of exactly this usage and the 
> idiom 'rdf:about=""' has been used in precisely this way.  
> May I suggest rewording such as "A second motivation is to 
> provide an alternative to the RDF/XML syntax that is simpler 
> to use when adding metadata to a document about the document itself."
> Section 1 Motivation, RDF/XML example: simple typo; the line 
> "<xh11:cite href=... />" should be <xh11:cite 
> rdf:resource=... />" (and, pedantically, the preceeding line 
> should also have the rdf: nsprefix on the 'about' attribute.)
> Use of '/' vs. '#' in examples.  There is much debate on this 
> point, none of which is particularly relevant to a reader's 
> understanding of the RDF/A draft.  TAG issue httpRange-14 [2] 
> is one of the current loci of discussion on this point.  I 
> recommend that in your examples you use '#' in any URI that 
> is not intended to refer to a document; e.g.
>   http://www.blogger.com/profile/1109404#
> (or ...#p if you think that looks better) rather than just
>   http://www.blogger.com/profile/1109404
> [2] http://www.w3.org/2001/tag/issues.html?type=1#httpRange-14
> Section 3.1 General Approach: I wrote the annotation "nice!" 
> next to the example where you first show the use of both rel= 
> and rev= on the same element.  Thought you'd like to know that ;)
> Section 3.1, next-to-last paragraph starting "However, RDF/A 
> provides another mechanism".  The end of this sentence reads 
> awkwardly; I read "then the [triple] concerns the parent of 
> the element" as "the subject of the [triple] is the parent 
> element itself."  It might also be appropriate to include a 
> forward reference to the term [context statement] introduced 
> in 4.1 to explain this concept.  This example would further 
> benefit from including the N-Triples produced by the RDF/A syntax.
> Improper usage of foaf:knows; starting with Section 3.3 (the last two
> examples) the examples take a shortcut and use mailto: URIs 
> as the subjects and objects of foaf:knows relations.  The 
> FOAF ontology specifies that the rdfs:domain and rdfs:range 
> of foaf:knows is a foaf:Person [3].  So, while there is a 
> sense in which you are correct in Section 4.2.2 saying that 
> these FOAF expressions are "valid", they certainly are not 
> recommended practice.
> [3] http://xmlns.com/foaf/0.1/#term_knows
> The concept foaf:knows has a certain pedagogical suitability 
> for the syntactic features you are trying to show throughout 
> these examples; however, it is also important that the 
> examples not be semantically misleading.  Ora and I tried 
> this shortcut in the first RDF specification (confounding 
> John Smith's homepage and the person known as John Smith) and 
> I have come to regret it.  A hack fix would be to use URIs of 
> the form 
> http://example.org/person/daniel.brickley@bristol.ac.uk# 
> instead of the mailto: URI.  This hack would still require a 
> disclaimer but it avoids propagating an important FOAF usage 
> misconception.  Perhaps Dan Brickley might suggest a 
> nicer-looking alternative that doesn't require introducing 
> bnodes except where you really want the bnodes for 
> illustrative reasons.
> Section 4.2.3 Using xml:id -- corner case; should it be 
> permissable to use an attribute of type xml:id and a nodeID 
> attribute on the same element?  If so, this probably means 
> simply that there is an owl:sameAs relationship [4] between 
> the two identifiers.  A similar question arises if about and 
> nodeID or an about and this xml:id attribute appear on the 
> same element.
> [4] http://www.w3.org/TR/owl-ref/#sameAs-def
> Section Using the [context statements]'s about 
> attribute: I believe there is a typo in the third chunk of 
> XML (the chunk in the Note); it seems to be misssing a 
> property='dc:title' attribute. Or there is some magic here.
> Section 4.4 Establishing the object:  As noted in 
> there is a third way to establish the object of a statement, 
> namely element content.  I suggest noting that option in 
> another subsection of 4.4 for completeness.  Then there is 
> the question of whether it should be valid to have both a 
> content attribute and element content.  It would complicate 
> the XML Schema to disallow both on the same element but the 
> simplest interpretation that occurs to me is that there are 
> two RDF statements with the same subject and predicate for 
> each of the (literal) objects.  Not sure if this is useful.
> -Ralph
Received on Friday, 29 October 2004 08:18:07 UTC

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