Thanks for the Snodgrass reference, it is rather similar and pre-dates
the book I was looking at. (Same notion of valid/transaction times,
but Date's non-SQL approach) From a quick skim it doesn't address the
distinction Date et al draw between historic and current temporal data;
however it looks very useful for mapping their concepts to SQL.
Eric
On Friday, Oct 15, 2004, at 20:25 US/Eastern, George Essig wrote:
> Eric D. Nielsen wrote:
>
>> 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.
>
> I have not read the book you mentioned, but I have read a book that
> may be related. I recommend
> looking at:
>
> Developing Time-Oriented Database Applications in SQL
> by Richard T. Snodgrass
>
> The book is out of print, but the author has made the PDF available on
> his website at:
> http://www.cs.arizona.edu/people/rts/tdbbook.pdf
>
> One of the main ideas in the book is to define valid time periods to
> record when information was
> true or visible. Valid time periods are implemented by adding 2
> columns to a table for the start
> date and end date of a period. Much of the book is about how to test
> for and resolve valid time
> period overlap between different rows. Topics include temporal
> versions of primary keys, inserts,
> updates, and deletes. I have implemented these ideas in PostgreSQL.
> I can talk further about
> this if you're interested.
>
> The last part of the book is about adding 2 more columns to a table to
> define transaction time
> periods. Transaction time periods can be used to reconstruct the
> state of a database at a
> specific point in time. I didn't read this part as closely and
> haven't implemented these ideas.
>
> Hope this helps,
> George Essig
