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!

Reply via email to