URL's are a subset of URIs, Universal Resource Indicators. I haven't
looked closely at the issue before, but it's all available at
http://info.cern.ch/hypertext/WWW/Addressing/URL/URI_Overview.html
In particular I think we'll make use of URN's:
URNs
There is currently a drive to define a space of more persistent names than
any URLs. These "Uniform Resource Names" are the subject of an IETF working
group's discussions. (See Sollins and Masinter, Functional Specifications
for URNs, circulated informally.)
It's hard to determine exactly where the discussion is at for this. There's
a mailing list for URI discussion at uri-request@bunyip.com, as well as a
hypermail archive at http://www.acl.lanl.gov/URI/archive/ I found a couple
interesting documents, but nothing declarative. It appears to be in IETF
territory now. One interesting suggestion for implementation of it is at:
http://www.acl.lanl.gov/URI/archive/uri-94q2.messages/0.html
written by "Ronald E. Daniel" <rdaniel@acl.lanl.gov>
The basic conclusion: it's being hashed out in other forums and isn't
something we have to worry too much about. Simply allow objects to
be referenced as URI's (which include and work like URLs) and we're fine.
Brian