Subject: RE: PFSP Proposal for 2 new keywords: Note of a FITSBITS post

From: "BARRY M. SCHLESINGER" <[email-masked]>
Date: Fri, 2 Jul 1993 18:26:20 -0400

The reason for the delay on this answer is that I was away at 
a meeting for over a week after this message came out and have just 
gotten back to clearing up back mail.

> Yet another recommendation of the OFSP meeting on 1993 Jun 16 was that 
> the OGIP change its use of the EXTNAME keyword, and that two new keywords 
> be introduced.

> The OFSP found that it was common practice within the OGIP to use the value
> of the EXTNAME keyword to simultaneously describe both the generic *kind*
> of dataset being stored, and additional *details* of the dataset. Thus
> values of the EXTNAME keyword were being formed by the concatination of 2
> or more sub-strings. This gives rise to long, and often user-unfriendly,
> EXTNAMEs essentially containing a variety of different pieces of
> information. 

Whilst such use of EXTNAME keyword is legal FITS, the OFSP proposes &
recommends the adoption/use of the two keywords listed below. Since this
is an issue likely to be of interest to the general FITS community, the
OFSP would welcome any comments (via FITSBITS) on this proposal. 

Furthermore due to the pressures imposed by currently flying missions
(ASCA, CGRO & ROSAT) there is an extremely urgent need for a convention for
these keywords within the OGIP (& High-Energy community in general). The
OFSP therefore plans to meet again in a couple of weeks to make its final
recommendations. Thus BITFITS subscribers are urged to response with any
comments etc on this timescale. 

THE PROPOSAL 
************

The OFSP recommends the use of the EXTNAME keyword be changed (at least 
within the OGIP), and that two new keywords, EXTCLASS & EXTTYPE be 
introduced:

EXTNAME   - Can be any string & is essentially not used by OGIP s/w
            (NOTE: IRAF can only cope with 6 character strings)
EXTCLASS  - Is a new string describing the sort of dataset stored (see below)
EXTTYPE   - Is a new string available to give more specific details on
            exactly what type of data is stored (see below)

A few examples should make the distinctions between the keywords more
obvious:

1) For various "Good Time Intervals"
   EXTNAME  = 'ABCBEF'          (or whatever you like)
   EXTCLASS = 'GTI'             (some sort of GTI is stored)
   EXTTYPE  = 'STANDARD'        (the GTIs from standard processing are stored)
or EXTTYPE  = 'ALL'             (all times when the instrument is on are stored
                                [no filtering has been applied])
or EXTTYPE  = 'UNKNOWN'         (uncertain what is stored)

2) For various "Events" lists
   EXTNAME  = 'GHIJKL'          (or whatever you like)
   EXTCLASS = 'EVENTS'          (some sort of EVENTS list is stored)
   EXTTYPE  = 'GOOD'            (accepted events [only] are stored)
or EXTTYPE  = 'BAD'             (rejected events [only] are stored)
or EXTTYPE  = 'ALL'             (all events [no filtering] are stored)
or EXTTYPE  = 'UNKNOWN'         (uncertain what events are stored)

The two new keywords follow a logical hierachy, solve all the current
problems, and seem general enough to give us (the OGIP, and general FITS 
community) flexibility in the future. 

----------------------------------- END ---------------------------------- 

Ian M George 					
NASA/GSFC OFSP
1993 Jun 17