xml-dev - Re: RDF and Resources

[Paul Prescod <paul@prescod.net>]

Dan Brickley wrote:
> 
> [...]
>  the optional fragment identifier, separated from
>    the URI by a crosshatch ("#") character, consists of additional
>    reference information to be interpreted by the user agent after the
>    retrieval action has been successfully completed.  As such, it is not
>    part of a URI, but is often used in conjunction with a URI.
> 
> So... on my reading...
> 
> --- the URI is the bit before the # in a URI or URI Reference
> --- the entire 'thing' picked out by a URI Reference might still be a
>         resource and have 'identity' (and might eg. have a first-class
>         URI in another scheme, eg uuid: or urn:). Even if just a section
>         of a larger object (video frame etc).

At the very best we can say that the thing following the # might or might
not represent "somehing with identity." There are no constraints on it. It
could be used to attach a stylesheet or make the background color of the
displayed object blue. It is merely "additional reference information."

Therefore I think that RDF is correct to limit itself to the two
Web-language where the referenced objects have identity (even if the
details are still being worked out in the Information Set project).

I think that even in the XML realm there is a problem. If XPointer-NG
continues to allow spans to be addresssed as first class objects (a
mistake IMHO) then that would mean that every possible start,end pair in
an XML document is a separate "resource". Iterating over these "resources"
within a document would be an impossibly slow operation.

A better model (that they will hopefully adopt) would be that spans
address NODE LISTS (not "span resources"). Then an RDF attachment could be
interpreted as shorthand for attaching to each node in the list. After
all, we desperately need this shorthand and it makes iteration easy.
Resources would correspond to what we think of as nodes: elements,
attributes, characters and so forth.

> When this wierdness in web architecture is cleared up, and the different
> renderings available (eg. over http, http-ng) are more explicitly
> differentiated, RDF and XML will be living in a happier less ambiguous
> world.

Agreed. Insofar as the grove model was designed precisely to clear up an
identical weirdness in SGML and HyTime, I tend to think that it is the
best place to start in fixing the Web.

-- 
 Paul Prescod  - ISOGEN Consulting Engineer speaking for only himself
 http://itrc.uwaterloo.ca/~papresco

"Silence," wrote Melville, "is the only Voice of God." The assertion,
like its subject, cuts both ways, negating and affirming, implying both
absence and presence, offering us a choice; it's a line that the Society
of American Atheists could put on its letterhead and the Society of
Friends could silently endorse while waiting to be moved by the spirit
to speak. - Listening for Silence by Mark Slouka, Apr. 1999, Harper's

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