[fitswcs] WCS documents

[Steve Allen]

On Tue 2001-10-16T09:21:32 +0100, Clive Page hath writ:
> It's factor (2) which makes one worried about adding a new TFORMn or
> TDISPn value (e.g. HMSw.d for sexagesimal formats) which would be the
> obvious way of adding this feature.  An old program which only expects the
> existing list of valid TDISPn values might fall over, because the current
> Standard says "only the format codes shown in table 10 are permitted".

Upon consideration that restriction seems rather strange.
It seems it might have been better if the wording were
"only the format codes shown in table 10 are *defined*".

In the case of TDISPn the consequences of encountering an unknown
field are far from fatal, for the datatype is known.  Any program
could easily choose an adequate ASCII representation.  The
more permissive wording would have permitted harmless test implementations
of sexagesimal TDISP syntaxes.

As a rule the standard should not deny the possibility of evolution,
and this particular case seems like a mistake.  Perhaps we should comb
through for other such cases in order to make a list of things needing
fixing during the next round.

This really belongs in fitsbits more than fitswcs.

--
Steve Allen          UCO/Lick Observatory       Santa Cruz, CA 95064
sla at ucolick.org      Voice: +1 831 459 3046     http://www.ucolick.org/~sla
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