I've always thought it a weakness of the XML model that resource boundaries were visible at all. In your example, the calls on doc() to cross resource boundaries are explicit.

When you're designing an XML database, deciding what information to put in one document can be a major headache (e.g. if you're managing hotel bookings, how should hotel bookings be grouped into documents?) I've always felt it shouldn't matter: there should be a single data hierarchy in which the resource boundaries are totally invisible.

I'm sure that's achievable, but the web architecture doesn't encourage it. For example, intra-document linking is handled quite differently from cross-document linking; most schema languages can only validate one document at a time, not a collection of related documents.

Michael Kay

Saxonica