IHDEA-IVOA-FRAMES (IVOACOORDS)

A collection of reference frames in common use in astronomy, organised by top-level categories (equatorial, galactic, etc). These concepts are used in VOTable's COOSYS, in SimpleDALRegExt's PosParam type, and of course in the Coords data model. Where no more precise reference are given, http://www.iaufs.org/res.html is often of help.