Hi Jeff,
I'll just finish off the Refractions tag-teaming of you :)
  I am writing from the Heart of Darkness itself, the ESRI UC, so I know 
whereof I speak, when I say: Jeff, free your mind! Do not confuse the 
particular terminology and implementation of a vendor with the application 
of a broader concept. ArcSDE versioning is a particular application of a 
form of spatio-temporal database schema. But it is not the only possible 
application, and it may not fit the needs of every user -- Chris has given 
some examples of change tracking which go well beyond the ArcSDE paradigm, 
but which *can* be supported through a well designed database schema.
  Remember, at root, all that ArcSDE "versioning" is, is a particular schema 
implemented in the RDBMS, and managed via the ArcSDE middleware. You can go 
into your ArcSDE geodatabase and interrogate the tables, see how they 
modelled the particular problem.
  Here in the Heart of Darkness, it is easy to forget that GIS transcends 
the particular boundaries and terminology used by ESRI, but it does.
Yours,
Paul


Quoting Jeff McKenna <mckenna@dmsolutions.ca>:

> I guess I was hoping to hear that PostGIS/PostgreSQL already handled
> spatial data versioning similar to ArcSDE.
> I understand the concept of 'meta tables' storing extra timestamp info,
> but are there examples of this already in use out there?  Has anyone
> been successful in implementing spatial data versioning with
> PostGIS/PostgreSQL????  (we deal with large datasets and this would
> impact the way we do things bigtime)
> 
> thanks.
> 



