RE: Personal reply to Edd Dumbill's XML Hack Article wrt W3C XML Schema

[Gavin Thomas Nicol <gtn@ebt.com>]

> Element types have specific semantics that don't very across instances. I
> would have thought that this would be one of the few universally accepted
> truths in the XML world (wishful thinking, I guess).

I think this depends on your notion of type. If I have an element containing
other elements in a specific order, I can give that combination a type
name "foo". If I have an instance that includes all of those elements,
plus an addition element, I can say that the instance extends the type
of the element, and I could give that derived type a name "bar" saying that
"bar" extends "foo" (type derivation by extension in XML Schema), or I
could simply say that the type of the element is "element content" for a
less restrictive type.

I think William was just pointing out that ad-hoc type extension is, in
fact,
very common in XML applications, and is one of the reasons for the success
of XML.