[fitsbits] start of Public Comment Period on CONTINUE Long Kwd convention

Thu Jun 25 11:03:25 EDT 2015

Overall I don't see much problem with this proposal.  Unlike the 
existing convention is requires no special keyword
so that long strings are possible in all headers if we incorpoate this.

However as pointed out by Ritchie I think that the text should describe 
how the comment fields
on an extended string are to be processed.  Should the comments be 
considered a single entity
in the same fashion as the strings.

There are also a couple of special issues that should probably be 
explicitly discussed.

   - Currently FITS strings cannot have significant trailing blanks 
since they are explicitly stripped.  However using the
long string convention it would be possible to support them using a 
construct like:

    WEATHER = 'ABC&'
    CONTINUE '  '
where the fact that we used the CONTINUE when all we put on it was 
blanks could be used to indicate that the blanks are significant. The 
inability is have significant trailing blanks is a minor but real 
deficiency for FITS keywords, and this could rectify it.  I am not 
advocating this, but I do think that this should be explicitly noted one 
way or the other.

If trailing blanks remain insignificant, then one can use
    WEATHER = 'ABC&' / Beginning of very long comment...
    CONTINUE '  &' / Continuation of long comment
    CONTINUE '  '  / End of long comment
as a convention for handling comments that don't fit in String fields.

Similarly one might have
    INTVALUE =     1 / Start of long comment
     CONTINUE         / Continuation of long comment...

for non strings.

  - The other issue is the meaning (if any) of  CONTINUE statements in 
any context other than being part of a long string.
I gave a possible example above, but

One language lawyer issue, is that I'd not explicitly note which 
keywords are not allowed to use this convention.  Rather I'd say 
something like:  Long string values may not be used in any keyword whose 
position is fixed within the FITS standard nor any that are required to 
be given in the fixed format.

I believe that would allow such keywords for TDISP, TFORM, TTYPE, and 
such  -- and I don't see why not.

If we are going to make long strings standard FITS, then we should make 
them first class values.

- I don't know if it would clarify things for users who have been used 
to seeing a LONGSTRN keyword to add an historical note of the form:

   When long strings were supported as a convention, the LONGSTRN 
keyword was used to
    signal the possible presence oflong strings in the HDU.  The use of 
this keyword is no longer
    required or recommended.

    Tom

Lucio Chiappetti wrote:
> ANNOUNCEMENT:  START OF FORMAL PUBLIC COMMENT PERIOD
>
> This is to announce the official start of a 3-week formal Public 
> Comment Period on the incorporation of the well known CONTINUE Long 
> String Keyword convention in the FITS Standard.
>
> This is part of a process to incorporate the most useful and widely 
> used registered conventions (which are valid FITS constructs) into the 
> official definition of the standard.
>
> The Public Comment Period on most of the "simple" conventions will be 
> opening simultaneously today or at latest next Monday. Please reply to 
> each topic separately mantaining the subject.
>
> The proposed text consists for CONTINUE
>
> - in the ADDITION of a new subsection 4.2.1.2 describing the usage
>   of the CONTINUE keyword to extend string keywords on several records
>
> - in the related editorial changes in section 4.2.1
> - in the addition of a short sentence in 4.1.1
> - in the addition of a cross reference in 4.4.2.4
>
>    and has been prepared by a technical team including L.Chiappetti,
>    W.Pence, A.Dobrzycki, R.A.Shaw and W.Thompson (main editor W.Pence).
>
> - If the proposal is approved also Appendix C will be updated listing the
>    new keyword, and a section H.3 will be added to Appendix H describing
>    the updates and the differences with the registered convention.
>
>    All the updates are shown in brick red colour in their current context
>
> The proposed draft text is available at 
> http://sax.iasf-milano.inaf.it/~lucio/FITS/Conventions/continue-upd2.pdf
>
> Supporting material is provided in the FITS Convention Registry at the
> following URL http://fits.gsfc.nasa.gov/registry/continue_keyword.html
>
> Considering that the convention(s) have been in use since several 
> years, are legal FITS, were discussed on FITSBITS when the conventions 
> were entered in the Registry and therefore their usage is well proven 
> (also for what interoperability is concerned), the Public Comment 
> Period is reduced to 3 weeks.
>
> Also the review by FITS Working Group Executive can be speeded up and 
> handled in parallel or quickly after the conclusion of the Public 
> Comment Period.
>
> Please review the text carefully and post any comments, criticisms, or 
> suggestions on the FITSBITS mailing list. 
> ==================================================================
>
> The Public Comment Period starts today 19 June 2015 and will last 
> formally for 3 weeks until July 9 included.
>
> ==================================================================
> Background information on the FITS approval process
>
> Under the "Rules and Procedures" of the IAU FITS Working Group, 
> http://fits.gsfc.nasa.gov/iaufwg/iaufwg_rules.html, the first step in 
> the official approval process of any FITS proposal will be a formal 
> Public Comment Period to take place on the FITSBITS mailing list. 
> After that the IAU FITS Working Group Executive will review the 
> results. Following that the IAU FITS Working Group will then conduct a 
> final vote to approve or disapprove the proposal.
>