Re: [xml-dev] Are people really using Identity constraints specifiedin XML schema?

[Jonathan Robie <jonathan.robie@datadirect.com>]

I did a survey of schemas a few years ago, and also came to the 
conclusion that this feature is very rarely used.

In my own applications, the reason for this is precisely the one that 
Mike Kay identified - identity constraints apply only to a single XML 
document, and what I really need to be consistent with is generally 
located in some other document or database. For instance, the product 
number in a document must match a product number in the set of products 
offered in a given database.

Jonathan