XML definitions for hyperlinks should be documented in the terms of that glossary if they are not already. The current uri.bunyip discussions between TimBL, Dan, Larry Masinter, Martin Duerst, et al are most illuminating. Something that locates a resource. Something that names a resource. If you can name it, it's a resource.
Different resources have different names.
A single resource might have multiple names. One way to interact with a resource is to obtain an entity that is a representation of the resource at a given point in time. This isn't smalltalk, it's webtalk. That's a clear as it gets.