IDs and databases (Was: determining ID-ness in XML)

"Champion, Mike" wrote:
> It's not just one spec, id-ness is exposed to users of XPath, XPointer,
> XSLT, XLink, and DOM.  More importantly, it's a widely used feature in real
> applications that use these specs, especially when an XML app is working
> with a database.

Really? How?

If you're using XML-enabled databases like Oracle, IDs are close to
useless. In the XML=>database direction, they're not guaranteed to be
unique across documents and therefore can't be used as keys in the
database.

In the database=>XML direction, there are two problems. First, they must
be unique within a document, but you could have clashes because a
document can be built from multiple tables with colliding key values.
Second, they're Nmtokens, which eliminates numeric key values.

Are they used in native XML databases for something at the database
level -- that is, other than just ID attributes?

-- Ron