GDSII format has been created by CALMA. Then CALMA has been bought by VALID (at
this time Calma software was replaced by Construct). Then VALID has been bought
by Cadence...

So normally, you have to ask to Cadence about "official" specifications.

Anyway, most of layout softwares use GDSII format, so all of them have the
specs "somewhere". These specs are not easily available, because the format is
not "human readable" and only the engineers who make the bridge between
internal format and GDSII have used it. And as almost all layout softwares
propose GDSII format, nobody has usually to go into the specs.

So if you already have a layout software with GDSII interface, maybe your
support will help you.

Jean-Francois Mainguet
mainguet@tcs.thomson.fr