[fitsbits] XTENSION = 'FITS' proposal

[Steve Allen]

On Mon 2002-04-15T12:57:10 -0400, William Pence hath writ:
> Stepping back a minute to look at the broader questions raised by this
> proposal, I think the biggest issue is that it would basically transform the
> FITS file structure from a simple linear sequence of HDUs into a
> hierarchical structure with HDUs within HDUs (within HDUs (within
> HDUs...)).  I worry about the impact that this fundamental change could have
> on existing software and existing applications libraries (like CFITSIO).

I'll venture another step backwards.

I believe that all of these schemes are attempts to use FITS as a
database.  The linear scheme more nearly resembles a traditional
Relational Database ("I've been told that there's another related
thing out there and I should be able to find it").  The nested scheme
more nearly resembles an Object-Oriented Database ("I can tell there
there's another related thing because I can see it right here").

I believe that the jury is still out on whether relational databases
or object-oriented databases are better at solving many classes of
problems.  I'll point out that the syntax of XML basically admits the
encoding of both approaches, so in that language the choice is left to
the implementor.

FITS might do well to admit the possibility of both while encouraging
the study of the parallels between the problems being solved in FITS
and the problems being solved by databases and XML.

--
Steve Allen          UCO/Lick Observatory       Santa Cruz, CA 95064
sla at ucolick.org      Voice: +1 831 459 3046     http://www.ucolick.org/~sla
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