Ross Singer writes: > > Identifiers identify; locations locate. > > I've been avoiding and ignoring this all day, because I wanted the > thread to die and we all move on with our lives. But Kevin Clarke > just quoted this on Twitter, and I felt I couldn't let this slide > by. > > Locations do not locate. Locations identify 'place'. They are > still identifiers.
I'm sorry that you're bored with this discussion, Ross, but it's important nevertheless. (So many important things _are_ boring.) All you've done here is shift levels. Locations _do_ locate, but of course the location is itself (at a higher level) a Thing, which can be identified. To say that a location identifies a place, while true, doesn't change the core points, which are: * a location doesn't identify the Thing * an identifier does 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. It is also true, though I think uninteresting, that the URLs in this example are identifiers of locations. But no-one (except metadata fiends such as ourselves) cares about locations in their own right -- everyone cares about the Things that are _found_ at locations. Sorry if this all seems rather didactic and patronising, but it seems important enough to lay out clearly. _/|_ ___________________________________________________________________ /o ) \/ Mike Taylor <m...@indexdata.com> http://www.miketaylor.org.uk )_v__/\ Archosaurs rule!