An LCCN is useful because I can use it to look up records in _multiple_ 
different databases.  I suppose that you will argue this is a form of 
"de-referencing", but it is not a canonical de-referencing, because I 
want and need to do it in multiple places. It is also not a 
de-referencing that can be _automatically_ done from the semantic 
information in the identifier alone (no matter how it's formatted, as an 
info: uri, as a http:uri, or as some kind of an identifier that isn't a 
URI at all).  And is useful despite this, it does not require 
automatically discoverable de-referencing, and since I need to look it 
up in multiple databases, and the particular databases are determined by 
my own local business logic, there's probably no way to make an LCCN 
identifier that is 'automatically' de-referenceable for my needs.

LCCN is also a useful identifier because it allows me to recognize when 
two records in the same database represent the same title.Or, for LCCN's 
an authority records, when two titles in my database are written by the 
same entity.  That doesn't necessarily involve de-referencing at all. So 
maybe that's an even better story.

That's one example, LCCN.  There are others, used in similar ways.


Ed Summers wrote:
> On Wed, Apr 1, 2009 at 12:20 PM, Jonathan Rochkind <[log in to unmask]> wrote:
>> I completely disagree.  There are all sorts of useful identifiers I use in
>> my work every day that can not be automatically dereferenced.
> How are they useful to you? I'm seriously just asking for examples
> here, not trying to start an argument.
> //Ed