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[fitsbits] Draft WCS Paper V: Time



 
 
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Old April 7th 09, 07:03 AM posted to sci.astro.fits
Rob Seaman
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Default [fitsbits] Draft WCS Paper V: Time

On Apr 6, 2009, at 6:41 PM, Robert Hanisch wrote:

This reference is a tribute to Peter Bunclark, I think, and in his
memory it would be nice to let it stand.



That is certainly sufficient justification. FITS and ADASS and IVOA
are certainly not overflowing with whimsy - a little poetry (Latin or
otherwise) can't hurt.

As a standards document I don't quite see how it helps anything,


That said, Astronomy is a field where the actions of the Vatican from
the 16th century are still in force. A normative standard should cite
normative references. It seems likely that nothing has superseded the
1582 reference. In addition to whimsy and poetry, this is likely
pedantically correct as a fundamental reference.

unless we had a FITS file somehow documenting the supernova of 1054,
or something like that.


It is not unlikely that such a file, for instance a table or
simulation, would be created and used within a research or outreach
context. The standard needs to support such cases. There is no irony
here.

But for such a thing, we do not need to understand TAI or whatever.


I'm not quite sure what you are saying. Astronomy is broad in space
and deep in time. It may seem quaint for FITS to wrestle with complex
issues of timekeeping in a nominally historical context, but FITS
should be applicable for a variety of proleptic use cases. The reach
of FITS should exceed our grasp.

The usual thing is to let the authors publish their version, and
then the
FITS commandos come in and distill it down into the formal language
of the
standard. It would be nice if this translation could be an identity
matrix.


For these issues the authors are the FITS commandos. If you are
suggesting that papers I-V are not normative, I'm not sure I agree
with that interpretation. Surely for a number of WCS issues the
"formal language of the standard" still resides in the published papers?

Arnold has already chastised me for finding the keywords to be
obtuse and
inconsistent, and he is relying on history in his rebuttal. OK, we
messed up
before, and to be consistent, we will mess up again. Doesn't
matter, it is
just a list of keywords. I just find it strange to represent "time"
as T,
TIM, or TIME. Or "center" as CEN, CENT, or CENTE. We accepted this
before,
so I guess we go with it.


If usage governs then the biggest issue is DATE-OBS. Many millions of
files (and more every day) contain a DATE-OBS that expresses only a
date.

Any standard is a trade-off between the descriptive (usage) and the
proscriptive (newly conceived architecture). I would suggest that the
paper should express the minimal set of keywords needed to address the
full set of astronomical use cases. These will prescribe the desired
new usage. In addition, the paper should describe the range of usage
known to exist in the community. Ideally there will be (some)
overlap, but historical precedence shouldn't overrule improving
timekeeping in the standard.

Whether keyword names are truncated is only a minor aspect of this.
Rather, tell people what their institutions ought to be doing, and
also how to interpret what other institutions ought not to be doing.

Rob
 




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