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On Wed, Apr 1, 2009 at 6:14 AM, Mike Taylor <[log in to unmask]> wrote: > As usual, an ounce of example is worth a ton of exposition, so: > > Suppose I always keep a PDF of my latest paper at > http://www.miketaylor.org.uk/latest.pdf > for the benefit of people who want to keep an eye on my research. > (Hey, it might happen!) Today, I have a PDF there of a paper with the > DOI 10.1111/j.1475-4983.2007.00728.x. Tomorrow, my new paper comes > out, and I replace the old one with a PDF of that new paper whose DOI > is 10.abcdefghij. I move the PDF of the old paper to > http://www.miketaylor.org.uk/previous.pdf > > Now, then -- the DOIs are identifiers: they are not in themsleves > dereferencable (although of course they can be used as keys for some > mechanism that knows how to dereference them). Each DOI always > identifies the same Thing. The URLs are locations: they are > dereferencable, but they do not give you any guarantee about what you > will find at that location. Two different days, two different papers. > Note that a single location (latest.pdf) contains at different times > two different Things. And note that a single Thing (the older of the > two papers) can be found at different times in two different > locations. In contrast, the same identifier always identifies the > same Thing, irrespective of what location it's at. Hoorah for examples! Assuming a world where you cannot de-reference this DOI what is it good for? //Ed