Space-Time Coordinate metadata schemata

[David Berry]

Arnold,
       I've just seen the changes to the explanation document which
describe projections. The approach you are taking in terms of separating
the descriptions of the coordinate systems from the projections seems very
sensible. It gives a clear picture of the inter-relations between
the various coordinate systems. I do not know if you have software yet
which will read and use the XML descriptions you have devised, but either
way, you may be interested in the Starlink AST library which takes an
almost identical approach to the problem of describing WCS (in terms of
providing a collection of coordinate frame classes which can be connected
together using a range of different Mappings). We've been using it now for
about 6 years and it has been very succesful. I'm thinking that it may be
possible to modify AST to understand the sort of XML descriptions you have
produced.

A brief description of AST, together with pointers to the full docs and
source code, is available at

http://www.ast.man.ac.uk/~dsb/ast/ast.html

David