Re: Draft: Universal Document Identifiers
Tim Berners-Lee (timbl)
Wed, 11 Mar 92 12:07:28 GMT+0100
Date: Wed, 11 Mar 92 12:07:28 GMT+0100
From: timbl (Tim Berners-Lee)
Message-Id: <9203111107.AA28084@ nxoc01.cern.ch >
To: Larry Masinter <masinter@parc.xerox.com>
Subject: Re: Draft: Universal Document Identifiers
Cc: peterd@expresso.cc.mcgill.ca, cni-arch@uccvma.bitnet,
>> Peter Deutsch's message <9203051920.AA14978@expresso.cc.mcgill.ca>
>> Actually, Mike Schwartz has suggested using CRC checksums,
> From: Larry Masinter <masinter@parc.xerox.com>
> You can do better than that by either:
> a) use a good digital signature (MD5 or Snefru or ...). [...]
> b) rely on something else that's unique, e.g., hostid + timestamp, ISO
> DFR's DORs, Object Identifiers, etc.
> We've been using 256-bit UDSNs and are happy with the scheme. I'm
> hoping we'll have a writeup together before next week.
Peter, USDN is your term, so you decide what is and isn't one.
However, a UDI I define to be something you can use to get the object. You can't
use digital signatures, or mail-style message-ids for that. You need some hints in
the identifier as to where to start looking. (We're talking scalable distributed
system here, no central hash tables allowed.) Knowing when you have a document that
you have the right document is a different problem, but with a good name space
(like x500) you can do both operations.
Tim