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

Thu Mar 10 10:07:54 EST 2016

OK, it's 22 years, not a quarter century:
http://heasarc.nasa.gov/docs/heasarc/ofwg/docs/ofwg_recomm/r13.html
But the convention as written has been used in millions of files since then.
As Peter said, it may, in hindsight, not be the most beautiful solution (and
if we were designing it today, we might have chosen your proposal), but it
works, and has been working for 20+ years, so let's just live with it.

Cheers,

  - Arnold

-------------------------------------------------------------------------------------------------------------
Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
--------------------------------------------------------------------------------------------------------------

On Thu, Mar 10, 2016 at 8:59 AM, Demitri Muna <demitri.muna at gmail.com>
wrote:

> Hi Peter,
>
> On Mar 9, 2016, at 4:13 AM, Peter Weilbacher <pweilbacher at aip.de> wrote:
>
> There is a standard here that is used in virtually every (every)
> computer language - continuation or concatenation characters are
> located outside of the string being quoted.
>
>
> But we are not discussing a computer language here, but a file format.
>
>
> I mentioned it as the convention will already be familiar to people. But
> whether it’s a file format or a computer language is irrelevant; the
> question what is easier to parse and/or read, first by a human and second
> by a computer. When one sees a line end with an ampersand and a single
> quote, the current proposal says “this might be a continuation character,
> or it might not.” When virtually every computer language agrees on a
> certain syntax, it’s worth paying attention to. Can anyone point to a
> counterexample where the continuation character is contained within a
> quoted string anywhere?
>
> I don't think that the FITS Standard allows to have anything between the
> value and the '/' that starts the comment. At least that's how I
> understand Section 4.1.1 and Appendix A. So having the continue
> character outside the string literals would make a very fundamental
> change to the FITS format. And quite hard on every FITS header parser.
>
>
> The current proposal specifically modifies Section 4.1.1, so that is what
> is under discussion. Given this:
>
> STRKEY = 'This keyword value is continued&'
> CONTINUE ' over multiple keyword records.'
>
> or this:
>
> STRKEY = 'This keyword value is continued' &
> CONTINUE ' over multiple keyword records.'
>
> an existing parser would treat the ampersand as part of the value and see
> no comment. I don’t see how this is a fundamental change or how it will
> break existing parsers. Can you provide an example where this would be a
> problem? You would never have this, for example:
>
> STRKEY  = 'string' & / comment
>
> This seems to be the edge case, where again the ampersand is not between
> the '/' and the comment, which is still not a problem:
>
> STRKEY  = 'some string that ends here but is followed by a comment' &
> CONTINUE '' / comment here
>
> If the motivation is to turn into a standard something that someone
> else decided ad hoc to do, then I’d ask if this really is the best way
> to define standards? The fact that one institute did something doesn’t
> necessarily make it the best idea, and in this case I really don’t
> think it is.
>
>
> The discussions about the CONTINUE discussion predate my time in
> astronomy as well, but if you read up on the convention's history, you
> will find quite a few messages to this list from 1993 and 94. So it was
> not decided "ad-hoc" at all, and not by one institute, either. (I think
> this is true for all the conventions that currently exist.)
>
>
> The oldest message on the web archive only goes back to March 1996 (which
> I note with amusement contains a message with the subject "[ANN] New FITS
> viewer for the Macintosh"). I mean ad hoc in the sense that it wasn't part
> of the format. But I think the argument that it was discussed a quarter
> century ago isn't a strong one; I am pointing out very specific reasons why
> this is not the best idea.
>
> I agree that this is not the most beautiful way to create FITS headers.
> But since the motivation here is rather to have an incremental
> improvement that works (we know, because it has seen usage for 20+
> years) instead of reinventing the FITS format, I agree with the
> proposal.
>
>
> I think this is a very important point. There has been a lot of discussion
> about file formats and pretty wide dissatisfaction with FITS. There's no
> question it's showing its age. I think it would be one thing if there was a
> commitment to properly addressing the real concerns with a proper FITS v2.0
> versus incremental patching. The past should guide the future, not
> constrain it.
>
> Cheers,
> Demitri
>
> _________________________________________
> Demitri Muna
> http://muna.com
>
> Department of Astronomy
> Le Ohio State University
>
> My Projects:
> http://nightlightapp.io
> http://trillianverse.org
> http://scicoder.org
>
>
>
>
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