XSchema Spec Section 2.2, Draft 1

[Ron Bourret]

Paul Prescod wrote:

> > The XSC:id attribute identifies the name of the element, and is required. 
> 
> I don't think that ID/IDREF is going to be powerful enough for us, 
> unfortunately. We will want to be allowed to reuse the same name for and 
> element and an attribute, for instance. So the name need only be unique 
> across a particular type. XML doesn't support this well, but a "linking 
> schema" language could (in the future) or some future version of XSchema 
> could support it directly. Michael Sperberg-McQueen described a nice 
> syntax for describing these kinds of constraints once.

This is a mistake in the current DTD, where we use id attributes for both 
ElementDecl and Notation (but not AttDef).  It's not quite clear to me if 
notations are in or out at the moment.  If they stay in, we could retain an ID 
attribute on ElementDecls and get uniqueness checking from validating parsers 
for free.  On the other hand, because a validator is looking like a reasonable 
application to build, there seems no reason to do this, since the validator 
would need to check uniqueness for non-validating parsers anyway.

Note also that attribute names are required to be unique only within the 
attributes of a single element, not all attributes.

-- Ron Bourret

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