Hi,
 
 
Decided to bite of GDTL and use it.  V nice, thanks etal.
 
I'm doing some bi-temporal stuff and need the concept of "beginning of time" and "end of time". 
 
A maximum and minimum ptime value in the ptime header or a limits header would do nicely.
 
Does this exist somewhere beyond my gaze or did it come out of the review?
 
Cheers,
 
 
matt.