W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > November 2001

RE: Issue rdfms-abouteach

From: Dan Brickley <danbri@w3.org>
Date: Fri, 16 Nov 2001 07:37:45 -0500 (EST)
To: <Patrick.Stickler@nokia.com>
cc: <dave.beckett@bristol.ac.uk>, <w3c-rdfcore-wg@w3.org>
Message-ID: <Pine.LNX.4.30.0111160721250.15883-100000@tux.w3.org>
On Fri, 16 Nov 2001 Patrick.Stickler@nokia.com wrote:

>
> > For writing by hand, there are, ahem, non-XML syntaxes that
> > are better.
>
> I'm not saying there aren't. But the spec defines an
> XML serialization and that is what the masses will use.
>
> IMO, anyone who things that the web community at large will
> adopt a non-XML notation for the interchange of RDF encoded
> knowledge is mistaken.

Heres a spin on things: this isn't just about interchange. The ability to
say about-each-ish things like 'all W3C employees have an interest in
technology'; 'all W3CRecommendations have a dc:format of text/html' etc is
useful both within RDF/XML documents that are exchanged, but also within
databases of RDF content. The aboutEach mechanism is useless for that
purpose, though this may not be clear to content producers.

We know from the past 3-4 years that content producers often have
difficulty thinking about RDF separately from its XML syntax. The
aboutEach mechanism is indeed a handy way of writing down in markup some
simple rules about common properties that apply to collections of
resources. If you know what you're doing. The real problem here isn't
about parsers, streaming etc., but about the risk of encouraging RDF
content producers to statically encode such rules in RDF/XML 1.0's
aboutEach syntax. By doing so, they are writing down
useful knowledge in a form that will (a) be lost forever when the markup
is parsed (b) be difficult to convert into more explicit rule and ontology
formats that can live in databases, behind APIs etc., since the authorial
intent behind these syntactic shortcuts will be invisible to automatic
tools.

I for one will never enourage people to write down useful generalisations
in aboutEach syntax, because I don't want to have them come back and ask
me why those rules aren't accessible via the (graph-oriented) APIs, query
languages, database interfaces etc that they'll have to use to access
their content. In my experience of talking to RDF developers _and_ content
producers, there's often misunderstanding about which features of the XML
syntax are carried through to the abstract graph. So my problem with
encouraging the use of aboutEach is that it risks creating a huge legacy
problem: information loss as we go from the RDF/XML into databases, APIs
etc. Because about aboutEach mechanism _appears_ to be RDF's way of making
generalised claims about members of a collection, people will likely use
it as such unless we attach a health warning. Once it becomes clear that
aboutEach is just a wierd macro mechanism, I believe it'll lose its appeal
to content producers.


Dan



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Received on Friday, 16 November 2001 07:37:53 EST

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