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Re: ISSUE: Using @id to set subject in RDFa (ISSUE-121)

From: Sebastian Heath <sebastian.heath@gmail.com>
Date: Sun, 20 Nov 2011 09:07:25 -0500
Message-ID: <CACsb_1pKtANQKAYHM++PXaQSq3nOEPPQ=enxZrPjxugkwRKKcA@mail.gmail.com>
To: RDFa WG <public-rdfa-wg@w3.org>
Thanks to Toby and Ivan for their responses.
Yes, it's a feature request, no doubt about that.
I'll take two approaches to further advocating the feature
andresponding to the comments so far.
1) I think it's important that rdf/xml supports a similar
mechanismwith its rdf:ID mechanism [1][2]. The full discussion is in
thatdocument so I quote only this from [1]: "rdf:ID provides an
additionalcheck since the same name can only appear once in the scope
of anxml:base value (or document, if none is given), so is useful
fordefining a set of distinct, related terms relative to the same RDF
URIreference." That would apply to the @id/@typeof combo in RDFa.
 And it's relevant that rdf:ID is widely deployed in the wild.
Inparticular, it's used in the skos and owl communities.
2) I reference skos and owl, in part, to move our consideration of
usecases beyond foaf based examples. I mean it as  a serious comment,
andnot a bit of snark, when I say that the semantic web is more than
justa rolodex. The semantic web instantiates lots of resources -
usingthat term in its rdf sense - that are concepts, not physical
thingslike people. It's here that the @id/@typeof combdo will
beparticularly useful.
 A potential use case: list of geographic co-ordinates in latitude/longitude.
 A geographic co-ordinate system is not a physical thing. And
norlocations specified in a co-ordinate system. Sure, you can use
thosepositions to get to physical place but there's a difference.
 So to markup one entry in a list using @id/@typeof is simple based
onthe w3 geo vocab and  [3] some other well-known vocabs:
 <div id="pos1" typeof="geo:Point"> <span property="dc:title">stop
1</span> <span property="geo:lat">55.701</span> <span
property="geo:long">12.552</span> <span property="rdfs:label">A nice
place to visit</span> <img rel="foaf:depiction" src="#image1"/> </div>
I think it's trivial to see which triples this would produce if
the@id/@type syntax is supported.
 It should be clear that markup such as the above is the
originalinstantiation of the concept being both identified and
described. Andis done in such a way that it is visible to both
dom-aware andrdfa-processor aware. I phrase it that way because for my
needs, thatis an answer to Toby's concern about "what is being
identified" and toboth Ivan's and Toby's concern about how this
overlaps withTAG/Semantic Web issues. Again, it is OK for RDFa to be
the originalinstantiation of a concept and for RDFa markup to support
thatinstantiation as a full node on the Semantic Web/Cloud of Linked
Data(in my case with a preference for Linked Open Data).
 And I think that the @id/@typeof syntax would be a simplificationover
the current syntax and so meets Ivan's concerns about richness.
 Perhaps personalizing too much, I have lots of use cases for
thisconstruct. I'm not just pushing it in abstract. Another one is
thepresence of bibliographic citations in born-digital scholarship.
Theassociation between an article and a source is usefully implemented
asan addressable node on the semantic web. This can be done by
enforcingequality between @id and @about but that's fragile in
comparison tothe robust and clear semantics of the proposed
@id/@typeof construct.
 -Sebastian
Received on Sunday, 20 November 2011 14:08:02 GMT

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