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   Re: [xml-dev] overrun with bohemians?

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From: "Miles Sabin" <miles@milessabin.com>

> Robin Berjon wrote,
> > if there's anything to learn from programming languages, it's clear
> > that it should *never* be enforced, and *never* be made necessary.
> Au contraire ... with programming languages typing should _always_ be 
> enforced and _always_ be necessary. If that causes you grief, then 
> you're probably using the wrong language.
I think we need to draw the line between different kinds of "typelessness".

There is 
    * late binding (where the information needed for typing is only available
     at the last minute)
    * reflection (where the object carries its type information around)
    * casting (where the language or some context forces a thing to be 
        treated a certain type)
    * generic operations (where, rather than a thing having no type, it 
        is deemed to have some very generic operations, such as equality testing
    * dynamic typing, where a value is looked at, and the type is selected from
        it according to lexical hints
    * typelessness, at an extreme where an operation occurs without any
    checking on some kind of memory location or a pointer. 

The occurrences of these in XML might be
    * late binding, such as in XML Schemas when you may access base
        types very late
    * reflection, such as using xsi:type to figure out the type
    * casting, such as where a query treats some text as a particular type
    * generic operations, pretty much what XML is without XML Schemas,
        wander around trees and look a strings.
    * dynamic typing, such as the = operation in XSLT

 I don't really see any typelessness at work in XML: it seems to be a property
of languages rather than data. 

Rick Jelliffe


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