Re: Namespaces, W3C XML Schema (was Re: ANN: SAX FiltersforNamespaceProcessing)

[Ronald Bourret <rpbourret@rpbourret.com>]

Elliotte Rusty Harold wrote:

> I am concerned that the theoretical use of schemas for typing is
> overriding their practical use for constraint checking.

The use isn't theoretical. Witness all the products that generate
classes from XML Schemas.

> Very few people
> are actually using schemas for typing. Instead they're being used for
> validation.

I think it depends on how you do the counting. Clearly, the number of
people validating schemas outnumbers the number of people writing code
that explores them. This is a restatement of the fact that the number of
document authors is greater than the number of programmers.

If you count applications, validators are a minority.

> In validation, we need local types (if not necessarily unqualified
> local types) because the W3C XML Schema Language confuses the two
> separate issues of typing and constraints checking, especially when
> it comes to complex types. I don't want to see any prohibition on
> local types enshrined as a best practice, or otherwise deprecated.

Could you explain this further? Isn't constraints checking either (a)
the checking of data against types, or (b) the definition of domains for
a given type? (I suppose this also depends on what you mean by "type".)

-- Ron