Utypes 0.4 comments

[Norman Gray]

Rob,

On 2009 Nov 25, at 16:55, Rob Seaman wrote:

>> For example, we might imagine utypes appearing in a FITS file like:
>> 
>> PFX01SSA= http://www.ivoa.net/...
>> PFX02STC= http://www.ivoa.net/...
>> UTYPE001= ssa:blah
>> ...
>> 
>> (see also Jonathan's suggestions in <http://www.ivoa.net/forum/dm/0610/1257.htm>).  But something like that would impose length limits on the sizes of prefixes and utypes as a whole: 'ssa:blah' could be at most 72 characters.
> 
> Presumably these would be represented as string valued keywords, in which case the limit is 68 characters.  An 80 character (ASCII 20-7E) card image total, minus 8 characters for the keyword, minus 2 characters for the value indicator (blank-equals), minus the 2 single quotes around the string literal.

Garhhh.  Arithmetic was never my strong point.  I'd forgotten about the quotes, but even then, 80 - 8 - 2 != 72...

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk