[fitsbits] Start of the CONTINUE keyword Public Comment Period

[William Pence]

Walter Jaffe wrote:
> While I think this is a useful convention, I note that this introduces
> an implicit ordering of FITS headers, i.e. they have to be read
> in a certain order if you want to interpret them correctly.  As
> far as I know, this is the first time such an implicit ordering
> has been introduced and it could conceivable cause some problems
> in copying/concatenating headers together.  There are of course
> a few explicit ordering conventions i.e. you have to start with
> SIMPLE = T.

Another case where ordering may be implicit is in a sequence of HISTORY 
keywords that document the order of data processing steps.  In some 
cases time stamps may have been added to each keyword to disambiguate 
the order.    This issue of keyword ordering was one of the main topics 
of debate back when this convention was first introduced back in 1993 
and 1994.

> I doubt this CONTINUE statement will cause much trouble in practise,
> but before approving it we might want to consider the more
> general problems of implicit ordering.

Keep in mind that the approval process for adding a convention to the 
Registry is mainly only designed to ensure that the documentation is 
clear and complete.  If a continuation convention were to be considered 
for the FITS Standard, then a much more rigorous and formal approval 
process would be required.

Bill Pence
-- 
____________________________________________________________________
Dr. William Pence                       pence at milkyway.gsfc.nasa.gov
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