[fitsbits] The CONTINUE and HIERARCH Conventions Public Comment Periods

[Don Wells]

Robert Hanisch wrote:
> ..I believe II share some responsibility for the invention of HIERARCH (I
> think I first suggested it at a FITS WCS meeting in Charlottesville, ca.
> 1989)..

I didn't remember who suggested the keyword HEIRARCH. I am not surprised 
to learn that it was you, Bob, and I am not surprised that the name 
HEIRARCH originated at that meeting. My memory is that the main purpose 
of that meeting (January 1989?) in Charlottesville was to discuss what 
we now call World Coordinate Systems, but we discussed many other ideas 
for FITS.

However, there is more to say about the origin of the HEIRARCH idea. The 
basic idea of a heirarchical namespace for FITS is ten years older; it 
dates from the time of the first FITS files in 1979, when Eric Greisen 
prototyped the idea in NRAO production software for VLA mapping. Two 
years later Greisen's implementation was illustrated in the original 
Wells-Greisen-Harten FITS paper in A&A June-1981, in Figure-1 on p.370:

INSTRUME= ‘VLA ' / NRAO(CV) VLA MAPPING.PROGRAMS
DATE-MAP= ‘16/10/78’ / MAP CREATION DATE DD/MM/YY
DATE = ‘27/05/79’ / MAP WRITiNG DATE DD/Vf/YY
ORIGIN = 'NRAO(CV) PGM=DEC2FITS(V1)’
HISTORY VLACV MAP METHOD=’FFT’ DATA=’OBS. VISIBILITY’
HISTORY VLACV MAP WCONU= O.00000E+OO WCONV= O.000000E+O0 TCONU= 0

Greisen used HISTORY in his implementations of the idea, as shown in the 
last two header lines above. His implementation allowed the possibility 
of more than one keyword=value on a heirarchical keyword line. What we 
have in the example above are internal variables and options for an 
imaging software package called VLACV. (This was before the AIPS 
project; the code was batch software running on an IBM mainframe; note 
the DATE keyword values.) The keywords are for the 'MAP' sub-namespace 
of the 'VLACV' package. Anyone who has ever looked at a header written 
by NRAO's AIPS package in the past 25 years knows that Greisen later 
used the same scheme for AIPS.

I have always regretted that Eric Greisen, Ron Harten and I did not 
include text in the original FITS paper that would have discussed those 
two header lines in Figure-1. I think that we should have advocated use 
of the heirarchical namespace idea by other astronomy groups.

-Don
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