I think the question might have been misread.  I understood the question to be, "is there or should there be a microformat for indicating that something IS an identifier", as opposed to "is there or should there be a microformat FOR identifiers".  E.g. given the string "urn:isbn:<whatever>", indicating that that string represents an identifier. I would suggest that the point of the identifier is that it represents some resource, and merely marking up a string as being an identifier doesn't accomplish much without being able to dereference it and obtain the resource it identifies.  Saying "urn:isbn:<whatever>" is an identifier doesn't do much good; the point is that given that identifier, I can tell that it's talking about a book and I can go obtain information about that book.  In which case, a href="" comes to mind.  I think there's room for some debate here. - David <div>On 11/23/05, Tantek Çelik <<a href="mailto:tantek@cs.stanford.edu">tantek@cs.stanford.edu</a>> wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Hello C. Hudley, welcome to the list! On 11/23/05 9:54 AM, "C. Hudley" <<a href="mailto:chudley@gmail.com">chudley@gmail.com</a>> wrote: > Has any work been done on a format for identifiers?  By "identifier" I > mean "some kind of arbitrary string that identifies the object at hand > in some system".  Examples of the kinds of identifiers that might be > in scope would be ISBNs for books, PMIDs for pubmed, node ids for > weblog entries, DOIs for journal articles, flickr ids for flickr > images, etc. Yes, this is a solved problem. See <a href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3986.txt </a> AKA Uniform Resource Identifier (URI). Thanks, Tantek _______________________________________________ microformats-discuss mailing list <a href="mailto:microformats-discuss@microformats.org"> microformats-discuss@microformats.org</a> <a href="http://microformats.org/mailman/listinfo/microformats-discuss">http://microformats.org/mailman/listinfo/microformats-discuss</a> </blockquote></div>