An example of similar is a CSS file being held as a decorative description for a whole site. I personally see XLink doing for linking, what CSS did for the average Web site. I guess I come back to the issue of link mapping being a resource and a consideration seperate in many cases from content, metadata, or formatting. They should be expressed in the document whose content they are. XLink is applicable.
Some links are metadata.
XLink is applicable. Some links are presentational decisions. They should be expressed in the stylesheet, and I hope that XSL will be up to this task.