Wide or Narrow Schema for VOEvent?

[Roy Williams]

Here is a question regarding the reporting of positional information for astronomical 
events. Should the reporting standard be

(a) Very Narrow,
meaning (for example) all positions in RA and Dec in ICRS frame seen from center of 
Earth in the format H:M:S/D:M:S? In this case it is easy for the event consumer to, 
for example, compute angular distance between two events. But it would be too narrow 
to report some events adequately (eg Martian volcano).

(b) Very Wide,
meaning that you can use galactic coordinates, or Jovicentric coordinates, or 
coordinates in equinox B1870.0, or Martian longitude/latitude. In this case, the 
event creator has wide freedom to use a natural coordinate system. But the consumer 
must be able to interpret something rather complex.

How do we compromise between these extremes?
Roy

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California Institute of Technology
roy at caltech.edu
626 395 3670