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

[William Pence]

I suggest we add the following restriction on the use of the CONTINUE 
convention:

"The CONTINUE keyword must not be used to extend the length of any of 
the mandatory or reserved keywords defined in this standard unless 
explicitly stated otherwise."

I actually think this restriction is not really needed (I trust users to 
not abuse the use of CONTINUE) but FITS has traditionally evolved very 
slowly and I don't think it hurts to be overly conservative in this case.

-Bill



On 4/12/2016 10:14 AM, Lucio Chiappetti wrote:
> ANNOUNCEMENT:  REOPENING OF PUBLIC COMMENT PERIOD
>
> This is to announce the reopening of a formal Public Comment Period on
> the incorporation of the long string keyword convention (aka CONTINUE)
> in the FITS Standard.
>
> A first PCP was held in June-July (started on 19 Jun 2015), and a second
> one in February-March (started on 26 Feb 2015).
>
> As soon as the IAUFWG was passing to the votes, a serious objection was
> raised and for this reason we are now re-opening the PCP until the issue
> is solved and agreed. The issue is explained below.
>
> 1 the original (optional) CONTINUE convention did not recommend its "use
>    with reserved or mandatory FITS keywords (e.g., TTYPEn or EXTNAME, or
>    other commonly used keywords ... [but only] for new application-specic
>    keywords, the values of which are not critical ..."
>
> 2 the text proposed in June strengthened this statement as "it must not be
>    used with the XTENSION, TFORMn, EXTNAME, TTYPEn, TDISPn, and TNULLn
>    keywords, and it is not recommended for use with any other string-valued
>    keywords that are defined in this Standard."
>
> 3 arbitrating among the arguments raised during the discussion, the text
>    submitted to the second PCP removed any explicit restriction, since the
>    technical team felt that it was generally sufficient to simply trust
>    that future FITS file creators will use the CONTINUE keyword judiciously
>    and only in cases where it is truly needed.
>
>    The edited text which was being submitted for vote is reported here
>    http://sax.iasf-milano.inaf.it/~lucio/FITS/Conventions/continue-rev2.pdf
>
> 4 it was questioned in particular by Mark Calabretta (whom I encourage to
>    submit any clarification and correction to this summary) that the
>    removal of all restrictions underestimated the impact on existing s/w
>    (in particular the WCSlib API), and it was de facto introducing a new
>    datatype
>
>    a the "Single record string keywords" defined in 4.2.1.1 correspond
>      to the "string" datatype as used so far.
>
>    b the "Continued string keywords" defined in 4.2.1.2 define a new
>      type which can be called "long-string"
>
> 5 it was proposed to add to the text a restriction 'CONTINUE may only be
>    used for keywords that are declared to have a value of type
>    "long-string".  It must not be used for keywords of type "string".'
>
> 6 the exact final wording is to be agreed, and this is the purpose of this
>    PCP.
>
> I will avoid to give here my own suggestions and opinions in this
> introductory summary, but will post them separately. I encourage anybody
> to review the issue carefully and post any suggestions, alternatives and
> comments on the FITSBITS mailing list.
>
>


-- 
____________________________________________________________________
Dr. William Pence    Astrophysicist     William.Pence at nasa.gov
NASA/GSFC Code 662     [Emeritus]       +1-301-286-4599 (voice)
Greenbelt MD 20771                      +1-301-286-1684 (fax)