Subject: AUTHOR --> CREATOR keyword

From: forveill at gag.observ-gr.fr (Thierry Forveille)
Date: Mon, 25 Oct 1993 17:57:29 +0100

William Pence writes:
 > The following describes a new FITS keyword that we plan to use within the OGIP.
 > As usual, any comments on this are welcome.
 > 
 > -Bill Pence
 > --------------------------------------------------------------------------------
 > 
 >                       Proposed CREATOR Keyword 
 > 
 > It is often useful to identify which software program created a
 > particular FITS file.  The reserved AUTHOR keyword has sometimes been
 > used for this purpose, but this is not consistent with the original
 > intent of the AUTHOR keyword to cite a publication.  Instead, the
 > following keyword should be used for this purpose:
 > 
 > CREATOR = 'program name'      / Program that created this FITS file
 > 
 > When appropriate, the value of the CREATOR keyword should also
 > reference the specific version of the program that created the FITS
 > file (e.g., 'WRITEFITS V3.2').  It is intented that this keyword should
 > refer to the program that originally defined the FITS file structure
 > and wrote the contents.  
There is a well established usage of the ORIGIN keyword for this purpose,
at least in the radio community. NRAO uses ORIGIN  = 'UNIPOPS u2f/1.3   '
for its single dish data and ORIGIN  = 'AIPS NRAO ' (quoted from memory)
for its interferometers, we use ORIGIN  = 'CLASS-Grenoble', and so on.
I would rather stick to this convention unless other communities use
ORIGIN for other purposes.

 > If a FITS file is subsequently copied largely
 > intact into a new FITS by another program, then the value of the
 > CREATOR keyword should still refer to the original program.  HISTORY
 > keywords should be used instead to document any further processing that
 > is performed on the file after it is created.
 > 
I can see many good reasons to try to keep track of the original producer,
but I am afraid you'll have a hard time getting computer programs to 
correctly decide that a FITS file has been left 'largely intact' (remember
most people don't use FITS as their internal format).

---

From: arots at xebec.gsfc.nasa.gov (Arnold Rots)
Date: Mon, 25 Oct 93 13:42:24 EDT

The NOST standard defines ORIGIN as "identifying the organization creating
the FITS file".  Notwithstanding what goes on in practice, I feel we should
try to stick with these definitions.  That means that either we have to
introduce a keyword like CREATOR, or redefine ORIGIN to also include an
identification of the software that created the FITS file.

  - Arnold Rots

---

From: tjp at bottom.caltech.edu (Tim Pearson)
Date: 26 Oct 1993 00:47:36 GMT

Re proposed CREATOR keyword (Bill Pence):
>HISTORY keywords should be used ... to document any further processing that

It seems to me that a HISTORY record is the most appropriate way to
specify the CREATOR information as well, unless a program that reads the
file needs to extract the CREATOR information. Off-hand I can't think of
any application where this should be the case; after all, the file is a
FITS file, and how you read it should not depend on what program was used
to create it. I suppose it might be important if the creator program has
bugs, however, and doesn't write a correct FITS file.

Tim Pearson
tjp at astro.caltech.edu

---

From: miller at lor.stsci.edu (Glenn Miller)
Date: Tue, 26 Oct 1993 02:38:09 GMT

>>>>> On 26 Oct 1993 00:47:36 GMT, tjp at bottom.caltech.edu (Tim Pearson) said:

>tjp at astro.caltech.edu

You are correct that such a keyword wouldn't be used to assert the
format of the FITS file. It could however tell you something very
important about the contents.

You would be interested to know what program created a file since that
tells you about what was done to the file. That is, there are any
number of reduction algorithms and knowing the program that was used
could tell you which one. For example, cosmic ray removal from CCD
images and image restoration techniques are two common reduction
problems which have a variety of algorithms available and no single
"right" answer. Not only might a human be interested in this
information (either to remember what s/he did last week or 3 years
ago), but another program might need this information to determine
what processing or reprocessing is needed.

I don't know if there are other FITS keywords which already fill this
role. I just want to point out that knowing what program (and in fact
what version of the program) can be critical to understanding the
scientific nature of a FITS file.
--

Glenn E. Miller                          miller at stsci.edu
Advance Planning Systems Branch          410-338-4738
Space Telescope Science Institute        410-338-1592 (fax)
3700 San Martin Dr. 
Baltimore, MD 21218 USA

---

From: Lucio Chiappetti <lucio at IFCTR.MI.CNR.IT>
Date: Tue, 26 Oct 1993 16:49:23 +0100 (MET)

> FITS file, and how you read it should not depend on what program was used
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> to create it. I suppose it might be important if the creator program has

   I do not agree in some extent.

   To me it matters if the file was created by the 'ESO-MIDAS' environment,
   or by 'KPNO-IRAF', or by my own XAS environment, or by a GSFC-OGIP
   program, because the conventions used depend on the environment, and
   I may need to massage the file to convert from such (known) conventions
   to my local environment conventions.
   So far I have assumed that one could use the ORIGIN keyword to do this
   (in case of MIDAS and IRAF any installation anywhere will put the 
   strings indicated above  ... and not e.g. IFCTR-MIDAS ... nobody is
   interested to know that a file was written using MIDAS at IFCTR or
   elsewhere).

   To me it does not matter to know which particular command was used to
   write the file (ORIGIN or CREATOR='intape/fits' or 'wfits', or
   'stwfits' won't tell me anything), although as a matter of routine 
   I record such information (and any manipulation) to HISTORY keywords.

   (If you want, the history matters to an human reader, not to a program;
   the "environment" matters to programs (be it expressed as ORIGIN or
   CREATOR), the "originating institutions" (in the sense of the place
   where the tape or disk drive was located) does not matter to anybody).

   I believe it is quite important to identify the "conventions" according
   which the file was written (via ORIGIN, CREATOR, EXTNAME, EXTCLASS or
   whatever)

---

From: hodge at stsci.edu (Phil Hodge)
Date: Tue, 26 Oct 1993 16:07:46 GMT

Bill Pence suggested a CREATOR FITS keyword to record the name of the
program that wrote the FITS file.  One disadvantage of a character-string
keyword rather than a HISTORY record is that a FITS reader does not have
to read more than the first eight characters of a character string, and
this is likely to be insufficient for many programs.

---

From: tjp at bottom.caltech.edu (Tim Pearson)
Date: 26 Oct 1993 16:36:50 GMT

miller at lor.stsci.edu (Glenn Miller) writes:
> I just want to point out that knowing what program (and in fact

I quite agree with this, but I think you need to know the entire processing
history, not just the first or last step. I don't think a single CREATOR
keyword is sufficient. I generally put the information in HISTORY records
(usually several records per step, to specify all the processing parameters
used). Of course, CREATOR will do no harm if used consistently by all
FITS writers.

Tim Pearson
tjp at astro.caltech.edu

---

From: phjj at ruchem.ru.ac.za
Date: Tue, 26 Oct 1993 18:37:29 GMT

>bugs, however, and doesn't write a correct FITS file.

It would be convenient to have a structured way of finding out what has been
done to an image.  I think NOD2 had/has some sort of mechanism like this.
Perhaps even some sort of enumerated keyword could be invoked, so the
total passage of an image through a suite of programs could be monitored?
Just an idea.

Justin
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