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   Re: XLink a special case in the self-describing Web?

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  • From: Paul Prescod <paul@prescod.net>
  • To: "Steven R. Newcomb" <srn@techno.com>
  • Date: Fri, 19 May 2000 14:52:35 -0500

"Steven R. Newcomb" wrote:
> Please correct me if I'm wrong about any of this.
> (1) XML Namespaces do not provide a way for a single element to
>     conform to an element type in each of several schemas.  Therefore,
>     there is no way for a single element to be recognized as
>     conforming to both the X:Foo and the Y:Bar element types.

You would not say directly that the element conforms both to X:Foo and
Y:Bar. You would rather s(in the schema) that the two are equivalent:

"""Through the new mechanism of element equivalence classes, XML Schemas
provides a more powerful model supporting substitution of one named
element for another. Any global element declaration can serve as the
defining element, or exemplar, for an element equivalence class. Other
global element declarations, regardless of target namespace, can be
designated as members of the class defined by the exemplar. In a
suitably enabled content model, a reference to the exemplar validates
not just the exemplar itself, but elements corresponding to any member
of the equivalence class as well. """

> (2) XLink is now just attributes; the element type can be anything.
>     This permits a single element to be recognized as an XLink and as
>     whatever else it may be.  (Whatever else it may be, it may still
>     only be one element type in one single namespace, as far as I
>     know.)  This is a kind of sleight-of-hand: XLink elements are
>     still XLink elements; we still expect certain combinations of
>     attributes to appear in certain contexts and not in others.

Theoretically XLink could use the equivalence class mechanism. So
yourlink would be defined as a "kind of" xlink. But I haven't tried it
so take that with a grain of salt.

 Paul Prescod  - ISOGEN Consulting Engineer speaking for himself
Just how compassionate can a Republican get before he has to leave the 
GOP and join Vegans for Global Justice? ... One moment, George W. Bush
is holding a get-to-know-you meeting with a bunch of gay Republicans.
The next he is holding forth on education or the environment ... It is
enough to make a red-blooded conservative choke on his spotted-owl
drumstick.     - April 29th, Economist

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