Following my post Developing an EPUB Linking specification a couple of months ago, a subset of the EPUB3 Working Group formed and has been actively researching and discussing the problem of EPUB to EPUB linking and EPUB identifiers in general. Based on feedback from others inside and outside that group, I’ve decided that many aspects of my initial proposal are flawed, but we’re now much closer to consensus on a proposal (or two) for submission to the larger EPUB3 Working Group.
You can see the specifics of the current proposals from the subgroup as they evolve on the EPUB3 wiki at PURL-based EPUB Identifiers and URI Links Proposal. Please comment there or on the epub-revision mailing list rather than here.
The aggressive publication deadlines for EPUB3 (fast approaching in Q1 2011) mean that this work cannot expand too much in scope, but I suspect that’s good motivation: we should try to understand and solve the most pressing problem(s) for EPUB to EPUB links and then get out of the way and watch the implementors & content creators.
Note: These early drafts on the wiki don’t represent the consensus of the EPUB3 Working Group.