The official programming interface for the PEX extension will be the official programming interface for PHIGS, plus the de facto or offical programming interface for PHIGS+. I don't know if ANSI or ISO is working on a CL binding for PHIGS, but ANSC X3H3.4 (Bindings) might be a good place to start. I can give you the phone number of the chair of that committee if you're interested in pursuing it.