audit trail, take 2

[Dave Peticolas]

David Merrill writes:
> 
> The xaction_id is not globally unique. If a record is edited 9 times,
> there will be 10 records with the same id. Once for the record
> originally created, and once for each edit.
> 
> The guid is globally unique. Each of these records would have different
> guids.

Right. What I meant was, can we make xaction_id globally unique
under the equivalence relation 

Transaction t1 == Transaction t2 iff t1 is an update of t2 or
                                     t2 is an update of t1?

So that xaction_id globally uniquely identifies the equivalence
class.

dave