RE: multiple types

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

> > I think people are getting confused between instances and type
> > definitions. In the context of a type definition, it makes great
> > sense to use "is-a" and "has-a" and "extends", etc. This is
> > again, defining the *type*, not an instance.
> 
> Are you saying anything different than there is a difference 
> between an XML document and a schema describing the document?

No. Thank's for being succinct :-) The point I was trying to make
it that these are logically orthoganal.

> Examplotron is something that blurs this.

I'm not sure that it does... or if it does, it's because of the
nature of XML type projection. I can say a document A extends
document B if document A has all of the elements and attributes
of document B in the same relative ordering.

In that case, the document sometimes acts as a schema, sometimes
as a document. I think the role distinction is important though
because it allows us to unify type projection no matter what
schema language is used.