[iaufwg] Appendix A, END keyword

[Steve Allen]

On Thu 2008-03-20T17:42:23 -0400, William Pence hath writ:
> The END keyword on the other hand is prohibited from having an '= ' in
> bytes 9-10, so it is not necessary to make it as a special case in this
> grammar.

I regret to admit that, among other mistakes, despite it always having
been illegal, there are FITS files written at Lick which have a "="
character following "END     ".

And in this regard I find myself wondering even further about Mark
Calabretta's wish for a listing of all the syntactic elements of FITS
which were once legal but which are now not legal.

Is it within our means follow the Jon Postel advice on internet
protocols in the RFCs and make the FITS standard into an
implementation guide detailing the conservative scope of what a FITS
writer MUST do and also the liberal scaope of what a FITS reader
SHOULD do?

The heuristics in various implementations of FITS readers (as only one
example, Doug Mink's FITS WCS reader) are far more liberal than the
any form that the standard admits.  Although that broad scope leaves
open the possibility of ambiguous interpretation, there are a lot of
applications where that is preferable to rejecting a FITS file which
does not strictly conform to the standard.  I'm not sure how we dare
go any farther than to leave a record of discussion in which we point
out that implementors may wish to consult particular existing code for
ideas on reading old FITS files.

--
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