I'm in the process of adding more historic information to one of my 
databases.  I've liked the theoretical treatment of the concept in 
"Temporal Data and the Relational Model", by Date, Darwen, & Lorentzos. 
  A lot of it is not realizable without a lot of user defined 
types/functions/etc.  I was wondering if anyone else has tried to use 
their approach as a base for their historical databases in PostGreSQL 
and has any "lessons learned" to share.
Thank you.
Eric Nielsen