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   Re: [xml-dev] many-to-many

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Seairth Jacobs scripsit:

> The Resource seems to me just a convenience for the server
> implementer, since the client can't know any more about than what it knows
> of URIs and Representations.  

That model works well when you are just fetching representations for human
or machine consumption.  When you want to make *assertions*, though, you
have a problem.  Consider http://www.heritage.org/images/shakespeare.jpg .
Now does that refer to *Shakespeare*, the playwright who was born on
or about 1564-04-23?  Or does it refer to a *picture of Shakespeare*,
which is in JPEG format and contains 176 by 190 pixels?  And if it refers
to one of them, how does one refer to the other?

It matters, because the assertions you can make about Shakespeare are
basically totally dissimilar to those you can make about a picture of
Shakespeare.  The picture has a (human) creator; Shakespeare doesn't.
The electronic picture was made in the 20th or 21st century; Shakespeare
was a 16th-17th century kind of event.  Shakespeare wrote in English;
Shakespeare's picture doesn't write at all.  And so on.  "The map is
not the territory."

Topic maps, for all their messiness, at least get this right: for each
assertion, you can tell whether it's about Shakespeare (a "non-addressable
resource") or about the JPEG of Shakespeare (an "addressable resource").
Topic maps talk about addressable resources using their URIs and a
resourceRef element, and about non-addressable resources using some
suitable URI and a subjectIndicatorRef element.  No chance of confusion.

RDF people could do this too, by only referring to addressable resources
with URIs, and using anonymous nodes for non-addressable resources
(with predications linking them to suitable subject-indicating URIs).
Unfortunately, the ideology of RDF doesn't work like that, although
technically it's feasible.  TimBL, e.g., is on record as saying
that the URI "http://www.w3.org/Consortium"; *is* the W3C for RDF purposes,
which leaves no URI for the text that describes the W3C.

Annoying little note: yes, I realize what I'm doing; no, it's not a mistake.

John Cowan   jcowan@reutershealth.com  http://www.ccil.org/~cowan
Most languages are dramatically underdescribed, and at least one is 
dramatically overdescribed.  Still other languages are simultaneously 
overdescribed and underdescribed.  Welsh pertains to the third category.
        --Alan King


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