[fitsbits] further reopening of Public Comment Period on the CONTINUE convention]

[William Pence]

Hi Walter,

On 4/21/2016 5:00 AM, Walter Jaffe wrote:
> A peculiarity of FITS keywords is that the order of the keywords in a header has no
> semantic meaning with the possible exception of SIMPLE=TRUE.  This indifference to
> order often causes some difficulties, but having been established
> as a practice, I think that it is a bad idea to introduce a new variant where
> the exact order of the CONTINUE statements is critical.

The FITS standard is not indifferent to keyword order and states (in 
section 4.1.1.1): "It is recommended that the order of the keywords in 
FITS files  be  preserved  during  data  processing  operations...". 
Thus, it would be bad practice to not  preserve the exact order of all 
the keywords.  In the 20+ years that the HEASARC and others have been 
using the CONTINUE convention in huge numbers of FITS files, I am not 
aware of a single case of the keywords becoming mis-ordered.

>
> I recognize the importance of being able to specify long strings but prefer
> either ad hoc solutions like those used to specify vectors:
>
> SVALUE1 = ' first part of long string '
> SVALUE2 = ' next part of long string '
> ...
>
> or puting these strings in an extension as an ascii or binary table.

Users can of course continue to use ad hoc solutions like this, but I 
hope you can still be supportive of projects that need a more robust 
solution for reading, writing, updating, and deleting long character 
strings in FITS headers.   Incidentally, the HEASARC required that long 
string values be assigned to keywords that already had an index number 
appended to the name, so your ad hoc solution of using index numbers to 
order the continuation keywords would not work for us.

regards,
Bill
-- 
____________________________________________________________________
Dr. William Pence    Astrophysicist     William.Pence at nasa.gov
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