All this buisiness about namespace URNs...

Kent Sievers ksievers at
Wed Jun 2 19:02:32 BST 1999

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 "" 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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