Subject: hierarchical keywords

From: thompson at serts.gsfc.nasa.gov (William Thompson)
Date: 8 Jun 94 19:18:41 GMT

A colleague of mine just showed me something that referred to a proposal for
hierarchical keywords in FITS files.  What is the status of that idea, and
where can I find a formal description of it?

Bill Thompson

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From: bschlesinger at nssdca.gsfc.nasa.gov (BARRY M. SCHLESINGER)
Date: 9 Jun 1994 09:16 EDT

In article <thompson.771103121 at serts.gsfc.nasa.gov>, thompson at serts.gsfc.nasa.gov (William Thompson) writes...
>where can I find a formal description of it?

	A discussion of the controversy about hierarchical keywords
can be found in the NOST FITS User's Guide, available electronically
by ftp from nssdca.gsfc.nasa.gov, directory fits, or in printed form
by request from nost at nssdca.gsfc.nasa.gov. 
	The controversy is over where the subordinate keywords should
be.  In one proposal, they begin in column 11 or later, following one
or more hierarchy names.  In the other, the hierarchy markers are on
separate lines, and all keywords begin in column 1.  Some installations
have implemented a version of the same line proposal, using the
HISTORY keywords as the top keyword of the hierarchy.  FITS readers
that do not support this convention will simply treat the entire line
as a comment, and no more should be expected of a general FITS reader.
There is an example in the User's Guide. 

				Barry Schlesinger
				NOST FITS Support Office