[iaufwg] [fitsbits] Start of the ''MBFITS" Public Comment Period

[Steve Allen]

On Fri 2007-05-25T15:34:17 -0400, Robert Hanisch hath writ:
> This topic came up in recent VO discussions, with the idea of using the VO
> registry to identify types of FITS files (e.g., this is an HST ACS image,
> version 7.2.1, and the keyword dictionary is located here [URL]).  In
> addition, each and every FITS file would include an IVOA Identifier that
> would point to its external definition.  All well and good, except that
> Arnold Rots pointed out that we have some millions of FITS files in
> existence that would not have these pointers.

It is my impression that FITS is rooted in text-based descriptions in
refereed literature, and as such FITS may never get to the point of
specifying any sort of IVOA Identifier per se.  I think FITS might get
to the point of specifying keywords with lists of IAUFWG-registered
tokens of the sort that this list of registered conventions could become.

In the context of the VO, the access protocol can either
1) supply all the meta-characteristics of the data externally to
the FITS file
or 2) insert the meta-characteristics of the data into FITS keywords
which were not in the originally archived files

I'm not sure which option makes most sense for various VO applications.

In the context of not-necessarily-VO visualization applications (like
ds9) which want to know how to read and display images which exist
only as FITS files on disk (or as URLs in the absence of VO protocols)
it is clear that IAUFWG agreement on the keywords and tokens to be
used with Option 2 is helpful.  So option 2 becomes yet another
convention to register with IAUFWG.

> It is fine for the community to know about FITS usage and keyword
> definitions.  Do please have a look at the the HST convention(s), if you
> want to call them that, at http://www.dpt.stsci.edu/keyword/.  The
> documentation is extensive and complex.  I would not expect the FITS
> community, or this committee, to review this documentation and approve or
> endorse it, even on the stated criteria of completeness, conciseness, and
> accuracy.

I think the IAUFWG should register the HST conventions, and all the
others, as a means of providing the background information necessary
for whatever future task force takes up the issue of how FITS can
interoperate with local conventions and VO mechanisms and applications
which may not have specific knowledge of either.

--
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