xml-dev - Re: All this buisiness about namespace URNs...

["Richard Anderson" <rja@arpsolutions.demon.co.uk>]

I do not follow this list anymore due to time etc, but this post caught my
eye.

I assume DCE UUIDs/MS GUIDs have been considered ?

----- Original Message -----
From: Kent Sievers <ksievers@novell.com>
To: <xml-dev@ic.ac.uk>
Sent: 2 June 1999 18:01
Subject: All this buisiness about namespace URNs...


Although I have listened to this list for many months, I almost never post
anything.

Three points:
1) If this is all about giving name spaces a unique name/ID in order to
avoid collisions, then there are dozens of ways of generating unique names
(I assume that nobody wants to be a registry).  For example, you could write
a program for the PC that would grab the machines processor ID, combine it
with the time stamp and convert it to base 64 and come up with a 16 digit ID
that could not be produced by any other PC at any other point in time. If
that wasn't human readable enough then you could add your own descriptive
text and still come in shorter than many URLs.  You would only need access
to a PC one time in the lifetime of the name space - to generate the ID/Name
that you would use.  This is just an example.  My point is that if you think
about it for very long at all, there are lots of ways of guaranteeing
uniqueness, even in a distributed fashion.  Especially if you are willing to
live with "unique enough."   Some other examples: use the hit count on a
special web site; have a "grab a tag" type web site that allows visitors to
generate unique tags; use one of the global LDAP servers to guarantee a
unique E-Mail address; have everyone open an account at the same bank and
use their account numbers; use a U.S. patent number (just kidding); etc.
etc. etc.

2) Are we really that worried about collisions?  After all, don't  I usually
know (and approve)  with whom I am exchanging data?  If I can assume that
the people I exchange documents with don't have a malicious intent, then
what are the odds that if I use "mynamespace.myproject.Novell.com" that I
will ever see any problems? Nil!  And if they are intending to collide with
me, then what recourse would I have anyway?  As a side note, it seams like
the harder problem is trying to actually collide and share an element.  For
example: my document has a "subject" while yours has a "topic."  Do we have
to generate large mappings in order to communicate with lots of different
systems?

3) When it comes to global identifiers, it seems to me that there are always
two distinct parts:  a) the objects name/ID that uniquely identifies it, and
b) the objects last known, or probable location.  My mail messages, for
example, have unique IDs, but they only help me find  the message by
including addition location information on where to look for it (which
message store).  The advantage of this type of scheme is: a) I can still
uniquely identify it no matter where it is moved, and b) if it is moved,
there may be some hope of searching for it and updating it's location.


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