A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » FITS
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

[fitsbits] Start of the CONTINUE keyword Public Comment Period



 
 
Thread Tools Display Modes
  #1  
Old July 12th 07, 08:54 PM posted to sci.astro.fits
William Pence
external usenet poster
 
Posts: 66
Default [fitsbits] Start of the CONTINUE keyword Public Comment Period

Rob Seaman wrote:
Perhaps the discussion from 1993 and 1994 could be included verbatim,
or linked by thread off the web page? I'd hate to hold a debate on a
topic that was already batted around a dozen years ago.


There is a link on the registry web page to the (very large!) set of
comments that were made about this convention when it was first
introduced, but the archived FITSBITS discussions for this time period
are just broken up into monthly text files. You have to scan through
the whole text file to pick out the relevant postings. It would take a
lot of editing to make a file just containing the CONTINUE thread.

Is the
registry page the entire text of the proposed convention? Like Tom
said, you need to cover the obvious corner cases, at least by
verbiage like "it is undefined what string is conveyed if a card
ending is '&' is not followed by CONTINUE".


What you see is the entire existing text of the convention, but I plan
to augment it with some additional text, based on the comments that are
made here during the public comment period.

1) Couldn't the reordering question be dealt with via appending &NNN
instead of &?

....
2) What is the reason for not strictly requiring that such a
continuation string end with ampersand-quote?

....

These are valid questions, but they are a bit 'off-topic' since the
purpose of the registry is to document existing conventions, not defend
the way they were designed. If we were designing a new continuation
convention now we might do things differently.

3) One suspects a number of conventions will depend on valueless
keywords.


Agreed. The ESO HIERARCH keyword (which will be submitted for inclusion
in the Registry in the near future) is another well known example that
is somewhat complementary to the CONTINUE convention. The HIERARCH
keyword convention effectively allows keyword names much longer than the
8-character limit of real keywords

The CONTINUE convention, however, is different in providing a more
general capability that could be used, for instance, within any other
convention. Deleting a CONTINUE card could in principle change the
meaning of any header in arbitrary ways.


As you further discussed in a subsequent posting, this CONTINUE
convention could be used in principle with any string-valued keyword,
including the mandatory or reserved keywords like TFORMn, TTYPEn,
EXTNAME. In practice, however, the continue convention has mainly only
been used for very instrument-specific keywords like

TDDES12 = 'D[0~3] & E[0~63] C[(S[msLimit1]~S[msLimit2]),((S[msLi&'
CONTINUE 'mit2]+1)~S[msLimit3]),((S[msLimit4]+1&'
CONTINUE ')~S[msLimit5])] '

I wonder if perhaps we
shouldn't rather be discussing how best to add this capability to the
core FITS standard.


This was one of the reasons for setting up the registry in the first
place. The first step is to simply document the existing convention in
the registry; as a second step, this may lead to a wider discussion of
how this sort of capability could be added to the FITS standard.

Back in 1993 when this convention was first discussed, we failed to
reach any consensus, largely, I think, because many people at that time
felt that there was no compelling need for any keyword strings longer
than 68-characters. In the rare cases where anyone need longer strings,
ad-hoc work-arounds were devised, rather than coming up with a general
solution to the problem.

Maybe this thinking has changed in the past 14 years(?). If enough
people agree that this is an issue worth addressing, it should not be
hard to come up with a technical solution for handling long string
keyword values (not necessarily identical to the current CONTINUE
convention) that could be considered through the official approval
process for inclusion in the FITS Standard.

Bill Pence
--
__________________________________________________ __________________
Dr. William Pence
NASA/GSFC Code 662 HEASARC +1-301-286-4599 (voice)
Greenbelt MD 20771 +1-301-286-1684 (fax)


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
[fitsbits] Start of the CONTINUE keyword Public Comment Period Rob Seaman FITS 1 July 15th 07 02:46 AM
[fitsbits] Start of the CONTINUE keyword Public Comment Period William Pence FITS 0 July 12th 07 07:41 PM
[fitsbits] Start of the CONTINUE keyword Public Comment Period Walter Jaffe FITS 0 July 12th 07 10:15 AM
[fitsbits] Start of the CONTINUE keyword Public Comment Period Peter Teuben FITS 0 July 11th 07 10:37 PM
[fitsbits] Start of the CONTINUE keyword Public Comment Period Thomas McGlynn[_2_] FITS 0 July 11th 07 09:57 PM


All times are GMT +1. The time now is 04:33 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.