The SECCHI instrument on the STEREO mission produces some files with table
extensions, and other files which don't. The value of the EXTEND keyword is set
to either T or F to account for this.


Steve Allen wrote:
On Mon 2007-08-20T01:00:32 -0400, Craig Markwardt hath writ:

Has EXTEND ever been optional for files with extensions?


Has EXTEND ever been relevant for FITS files at all?

I would like to know of any applications which actually use it.

If I am not mistaken the CFITSIO toolkit always sets EXTEND to true.

In my experience there are two types of reading applications:
Apps which don't know what they would do with an extension, don't even
look for them, and don't care whether EXTEND is set or not.
Apps which know that they are expecting extension(s), don't care
whether EXTEND is set or not, and may fail with an unhelpful message
if they do not find the particular extension(s) they seek.

So what applications are there, other than fv, which do not a priori
know what they are expecting when they read a FITS file?
In particular, are there any which, when they find extensions, actually
take different actions based on what they discover?

These are the sorts of questions which prompted the FITS MIME effort,
and the sorts of questions which we realized we could not address there.

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