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Re: What are Semantics? (Was: Serving generic XML)

From: Tantek Çelik <tantek@cs.stanford.edu>
Date: Mon, 19 Aug 2002 18:57:16 -0700
To: Nicholas Atkinson <nik@casawana.com>, www-tag@w3.org, www-style@w3.org
Message-id: <B986F00B.15648%tantek@cs.stanford.edu>

Certainly XHTML is not one size that fits all.  It just so happens people
produce a lot of (semi)linear text documents with hyperlinks which XHTML is
particularly well suited for.  However, there are also semantically richer
languages like MathML, and languages like SVG more appropriate for
information (e.g. maps) that is structured two dimensionally.  Or for
information that is structured temporally there is SMIL.

I don't think RDF does/cando what you think it can.  The only equivalent of
"TDF"s we have currently are the prose of the abovementioned
language/vocabulary specifications.

In the near future, Schemas could act as "micro-level" TDFs, and in fact,
there is work to produce Schemas for the modules of XHTML Modularization[1].
Similar efforts to produce schemas for these other semantically rich
languages would probably be helpful.  Perhaps over time Schemas can evolve
to describe higher level data/content types (i.e. more than just
hierarchies/aggregations of simple data/content types), eventually reaching
the point where you can describe that a <headline> tag means "a header" in
an XSD.

But until we reach that point (and perhaps even for some transitional
period), we will need to continue to specify semantically rich vocabularies
one at a time, using prose definitions in W3C specs.



On 8/19/02 5:44 PM, "Nicholas Atkinson" <nik@casawana.com> wrote:

> The "prescriptive" approach of saying that everyone should use XHTML is one
> approach.  However many people don't like being prescribed to!  And one size
> doesn't fit all.
> Another approach, perhaps more "enabling", would be to say that we recognise
> that XML + CSS style only gives a UA _part_ of what it needs (it is not
> sufficient for
> accessibility, for instance), and that authors need some (machine-readable)
> way of publishing what their XML tags mean.
> UAs would be able to retrieve/cache this "XML Tag Description file" in the
> background and would be able to determine definitively that in a specific
> document "<headline>" is "a header" (provided that "a header" is one of an
> agreed set of "meanings" managed by a central authority or organisation such
> as the w3c).  The UA would then be able to provide the appropriate
> accessible rendering.  (and clearly there are other applications too.)
> All we would need is an agreed (presumably XML) syntax for this "Tag
> Description File" and, crucially, an agreed set of standard "meanings".
> This set of standard meanings could be far richer than the semantics that
> XHTML supports.
> Obviously, the more subtle the meaning, the less likely it is that it could
> possibly be agreed upon.  But for meanings such as visual conventions like
> "a heading", or non-visual meanings such as "a patient", "a dentist", "a
> credit card number", "a longitude and latitude", "a temperature" or "a
> flight number" it is pretty clear-cut and unequivocal what they mean.
> Indeed we could have hierarchies of such meanings, or rather "ontologies".
> But hang on, such a "Tag Description File" already exists!!!!  Isn't this
> the kind of thing that RDF can/could do.
> So, after that lengthy preamble, my point is that instead of going down the
> XHTML route (which doesn't lead anywhere) why don't we "cut to the chase"
> and go down the XML + CSS + RDF route.
> RDF (or something similar) could be used by UAs to determine the "missing
> knowledge" required to produce accessible renderings and in a whole host of
> other applications, because it would indicate to UAs what the tags "mean".
> Isn't that the whole point?
> nik
Received on Monday, 19 August 2002 21:48:09 UTC

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