Re: [Scrollkeeper-devel] Unique identifiers

[Dan M. <d-...@uc...>]

On Tue, 28 Nov 2000, Ali Abdin wrote:

> * Dan Mueth (d-...@uc...) wrote at 01:20 on 28/11/00:
> > > We talked about this issue previously and we thought about an ISBN like
> > > ID generated by a server available throughout the internet. This server
> > > would generate unique IDs on request by document creators.
> > 
> > Alan and Daniel were kind enough to pop in on IRC to discuss scrollkeeper
> > yesterday and the conversation quickly moved to UUID's.  They recommended
> > (as Ali does) creating a UUID for each unique document.  Here a unique
> > document is probably a {doc, version, language, format} quadruplet, or
> > possibly even a superset of this.  It should uniquely specify the
> > resource.  We will need to decide where this belongs in the OMF, perhaps
> > an attribute to IDENTIFIER (ie. IDENTIFIER.UUID).  The UUID will be the
> > database key.  To make things simple, we can ship a script which generates
> > a UUID with scrollkeeper.  For systems with uuidgen, it will use that.  
> > For other systems, we may want it to request one from a server which runs
> > uuidgen (as suggested by Ali).  
> 
> It is important to point out that the UUID should not change for each
> /version/ of a doc. If you have a doc and then update it, it will have the
> _SAME_ uuid but a diff. version number, in my opinion. (by default, if you
> just use UUID you will get the "latest" doc.)
> 
> Also - different formats should have the same UUID. They are the same
> document, so they will have the same _METADATA_ (i.e. same author, same
> version, same category, etc.)

One of the reasons we want a UUID is as a database key.  So it needs to be
unique between multiple versions, formats, or languages of a document. 

We also want to guarantee that any two resources with the same UUID are in
fact the same.  I'm not sure how we will want to handle multiple
references to the same resource, but we will want to know if two resources
are identical or not. This will be particularly important if we are ever
merging multiple databases because you will have situations where both
databases will refer to the exact same resource (although they may have
different IDENTIFIERs.)  This is the reason for modifying the UUID for
each version.

I don't know if we would ever want to have duplicates of a resource in a
database. (eg. http://www.foo.org/faq.sgml and
file:/<stuff>/faq.sgml)  If this were the case, the database would need to
use a key which combined UUID with a code generated from the IDENTIFIER.

This is leaning slightly back to my original idea of basing the database
key on the URL, but Alan and DV insisted that URL was not a good key and
that we should use UUID's instead.

Dan