The W3C XML Core Working Group has posted the first public working draft of xml:id Version 1.0. This describes an idea that's been kicked around in the community for some time. The basic problem is how to link to elements by IDs when a document doesn't have a DTD or schema. The proposed solution is to predefine an xml:id attribute that
would alays be recognized as an ID, regardless of the presence or absence of a DTD or schema. There are a few issues with the spec as currently written, which I've been sending to the working group as I discover them, but the basic idea seems solid.