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Re: QName URI Scheme Re-Visited, Revised, and Revealing

From: Sean B. Palmer <sean@mysterylights.com>
Date: Thu, 23 Aug 2001 10:36:33 +0100
Message-ID: <009701c12bb7$717b4c80$e9da93c3@Palmer>
To: <Patrick.Stickler@nokia.com>
Cc: <www-rdf-interest@w3.org>, <www-rdf-comments@w3.org>
[Snipping uri@w3.org]

> Uhhh... so even if the NS spec says X and Y are different,
> RDF can do whatever it likes with them, including saying
> X = Y [...]

Of course it doesn't say that two names are equivalent; it simply uses the
QNames to form URI references.

[...]
> If potentially four lexically distinct QNames (i.e. two QNames
> which collide on direct concatenation used both for elements
> and global attributes) are merged by RDF into one single URI
> derived by the present RDF function, then how can you possibly
> make statements about them to differentiate them [...]

Er, perhaps using the URI scheme that you just invented? Once again, the
RDF model does not keep the QNames in the syntax as QNames. The RDF model
simply uses those QNames to form URI references. It doesn't keep the QName
information because it is irrelevant; we are not using QNames on the
Semantic Web, we're using URI references. And if you want to identify
QNames, partitioned and all, well we have your URI scheme for that.

The weird thing is that for years no one had had a problem with this. That
doesn't necessarily mean that people have understood it, I agree, but no
one has had a problem implementing the QName concatenation thing that RDF
does, and no one has moaned that RDF violates any Web axioms, and there are
a lot of people at the W3C who would do just that if they thought the
slightest little rule was being broken. It's not as if the people who came
up with the concatenation mechanism weren't aware of exactly what was going
on.

> But then we get that nasty problem of element and global
> attribute QNames having identitical semantics according
> to RDF's condensed serialization syntax [...]

Once again, it does not declare the QNames to be identical. It simply uses
the QNames to form URI references.

> [...] If I can't rely on *every* RDF engine used by every
> SW agent to interpret my data exacly as I have defined it,
> then the SW has no data integrity. Again, its about global
> consistency of data.

But all data on the Semantic Web are resources, which may be identified by
URI references. Perhaps you are getting confused that XML has no inherent
semantics, and that therefore is not the primary candidate for the Semantic
Web? ON the Semantic Web, all knowledge is grounded in URI space, not XML
space. The fact that it gets *serialized* into XML for transfer is
incedental, and you should not get hung up on the fact that the
serialization involves using QNames to form the URIs... and yet you seem to
get hung up time after time.

> [...] However, since people are already thinking in terms
> of QNames when defining their Web based ontologies,

What??? That's blatantly false! Show me one ontology that uses QNames; one
couldn't even easily represent QNames in RDF until your URI scheme or my
model came along, and yet there are plenty of instances of RDF using URI
references on the Web. And yet you claim that people are "already thinking
in terms of QNames when defining their Web based ontologies"?

> Folks using XML *think* in terms of QNames insofar
> as their data models, vocabularies, and ontologies are
> concerned.

I'll bet that not many XML developers really understand much about
namespace partitions and so on.

> [...] The fact that there is *not* an official, standard
> URI representation for QNames is what is surprising...

Well, no one has really had a use for it, so not really.

[...]
> > Using the concatenation mechanism is an excellent and
> > quick way to form those URIs out of QNames.
>
> Quick? Maybe. Excellent? No!
>
> It was a very clever hack that works with HTTP URLs
> using HTML fragment syntax, [...]

I think you'll find that a) FragID syntax is independant of URI scheme and
MIME type, and b) the "hack" works with a wide range, indeed a gross
majority of URI schemes. The only condition is that predicates used in XML
RDF end with an XML name character. That's it. And as soon as one can
easily express equivalences, *and* choose what URIs to use for properties,
it's not much of a problem!

> It also does not maintain lexical distinctions defined by the
> NS spec, and for that reason alone, its validity is suspect.

The NS specifications says nothing about what processors should do with
QNames, it simply defines what QNames are.

> If it's not standardized and mandated for all RDF applications, it's
> not a solution to the present problem(s).

It's just a new URI scheme, and URIs are opaque. All RDF applications
already handle it.

> Parentheses and escaping should do just fine [...]

Cool.

--
Kindest Regards,
Sean B. Palmer
@prefix : <http://webns.net/roughterms/> .
:Sean :hasHomepage <http://purl.org/net/sbp/> .
Received on Thursday, 23 August 2001 05:38:10 GMT

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