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

[Tim Pearson]

On Jun 19, 2015, at 3:07 AM, Lucio Chiappetti <lucio at lambrate.inaf.it> 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.

A couple of comments:

1. "It is recommended that the order of the keywords in FITS files be preserved". Can we not say that the order of "commentary" keywords,  CONTINUE, COMMENT, and HISTORY, is significant and MUST be preserved? (i.e., any reader that interprets these records must do so in the order in which they are presented). A reader that shuffles CONTINUE keywords is broken. The associated text in 4.1.1 says CONTINUE is only a convention, but with this change to the standard it is not.

2. I don't see any limit specified on how long a continued string can be. Shouldn't the standard specify some minimum a conforming reader should be able to handle, e.g., 1000 characters, or 2^32 characters?

3. "Also, any ‘orphaned’ CONTINUE keyword records should be interpreted as containing commentary text in bytes 9 – 80 (similar to a COMMENT keyword)." I strongly recommend making orphaned CONTINUE keywords illegal; their presence almost certainly indicates an error on the part of the writer which should be flagged by the reader.

Some opinions:

1. I'd really like to see some standard way to tag a FITS file with the version of the standard that it is following, now that we have multiple versions.

2. Although I welcome this long string convention, I'd prefer to see the standard find a more general way to allow any header record to span more than 80 characters. "Another technical team has been considering a *new* convention for long keyword name and extended character set. Since this is a new proposal, it will be most likely announced for a Public Review Period later and  separately." Shouldn't we wait for this? Will it be compatible with the CONTINUE convention?

3. I'd prefer to see commentary on previous versions of the standard that is irrelevant to someone implementing the standard moved to an appendix on "changes to the standard" (e.g., the new text "Earlier versions of this Standard only defined single string key- words as described in the previous section. The Standard now incorporates a convention (originally developed for use in FITS files from high energy astrophysics missions) for continuing ar- bitrarily long string values over multiple consecutive keyword records."). A standard should be a formal, precise, and concise document.

Tim

Timothy J. Pearson
Research Professor in Radio Astronomy
Cahill Center for Astronomy and Astrophysics
Mail Code 249-17, Caltech, 
Pasadena, California 91125, USA
E-mail:    tjp at astro.caltech.edu
Telephone:   +1 626 395-4980    




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