Please use Space Time Coordinates.

The STC system for astronomical coordinates and regions is an IVOA recommendation, and therefore we will all gain through interoperability. This interoperability is not just for technical systems, but also so that concepts learned in one area of VO can be applied in other areas. STC is applicable in many areas: ADQL, footprints, TAP, VOEvent, SIAP, source VOTables, etc. If a WG is intending to make a different representation of coordinate or region, they should explain why they are diverging from a standard already agreed. Further, the new representation should be simply and transparently convertable to STC to promote interoperability.

Identifying and using a single VO standard for space/time coordinates seems a foregone conclusion. The alternative would be chaotic, non-interoperating systems and software, which would confuse our users and annoy our sponsoring organizations. STC has been adopted as that standard - more to the point, no other option has been suggested. The sooner we begin to understand, use, and evolve STC (as appropriate), the better. This also ties in closely to the recent adoption of new IAU coordinate systems, see for example: http://www.adass.org:8080/Conferences/2007/Venue/people/participants/abstract?abstract_id=234. When the notion of sidereal time is no longer valid, clearly some new software framework is needed for coordinates. (RobSeaman)

Comment by ChristopheArviset
This topic has been made more generic and has been included in the Indicate inter-dependencies between IVOA Standards topic.