Following up on his earlier post (which was also blogged to CrossTech here), Leigh Dodds is now proposing the possibility of using machine-readable auto-discovery type links for DOIs of the form

<link rel="bookmark" title="DOI" href="http://dx.doi.org/10.1000/1"/>

These LINK tags are placed in the document HEAD section and could be used by crawlers and agents to recognize the work represented by the current document. This sounds like a great idea and we’d like to hear feedback on it.
Concurrently at Nature we have also been considering how best to mark up in a machine-readable way DOIs appearing within a document page BODY. Current thinking is to do something along the following lines:

<a href="http://dx.doi.org/10.1038/nprot.2007.43">
<abbr title="Digital Object Identifier">doi</abbr>:
<abbr class="uri" id="doi" title="info:doi/10.1038/nprot.2007.43">10.1038/nprot.2007.43</abbr>
</a>

which allows the DOI to be presented in the preferred CrossRef citation format (doi:10.1038/nprot.2007.43), to be hyperlinked to the handle proxy server (http://dx.doi.org/10.1038/nprot.2007.43), and to refer to a validly registered URI form for the DOI (info:doi/10.1038/nprot.2007.43). Again, we would be real interested to hear any opinions on this proposal for inline DOI markup as well as on Leigh’s proposal for document-level DOI markup.
(Oh, and btw many congrats to Leigh on his recent promotion to CTO, Ingenta.)