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   Re: [xml-dev] [permathread:semantics] What Markup Is For

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W. E. Perry scripsit:

> Quite simply, what datatype something 'is' is a corollary of that something
> being manipulated as of that type by a process. Type--and not just
> datatype--as opposed to labelling, inheres in process and not in the
> text or data submitted to processing.

This view of typing is common enough, but IMHO goes beyond necessity.

The RNG view of a datatype is that it is simply a pair of boolean
functions on strings:  isFoo(string) is true iff string is a syntactically
sound representation of the type Foo, and sameFoo(string1, string2) is
true iff string1 and string2 are interchangeable representations of Foo.
No notion of "objects of type Foo" is or need be introduced.

And in fact this is almost the whole work that XSD can do with types
as well.  About the only remaining notion is a second-order function
which asks of two types Foo and Bar whether every representation of Foo
is a representation of Bar as well.

With techies, I've generally found              John Cowan
If your arguments lose the first round          http://www.reutershealth.com
    Make it rhyme, make it scan                 http://www.ccil.org/~cowan
    Then you generally can                      jcowan@reutershealth.com
Make the same stupid point seem profound!           --Jonathan Robie


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