Subject: underscores and hypens in keyword names

From: pence at tetra.gsfc.nasa.gov (William Pence)
Date: Fri, 30 Jul 93 13:46:08 EDT

The OGIP FITS Standards Panel (OFSP)* recently made the the following
recommendation to use underscores rather than hypens in keyword names
used in FITS files created by the OGIP.  A copy of this recommendation
is being posted here for information to other groups who may be
interested in adopting a similar policy.

*The OFSP is comprised of members of the NASA/GSFC Office of Guest
Investigator Programs (OGIP). Its role is to coordinate and define
standards for the FITS formats used for the High Energy Astrophysics
datasets that are generated within the OGIP.

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 OFSP Recommendation on the use of Underscores and Hyphens in 
       FITS Keywords and FITS Table Column Names

The use of hyphens is discouraged in FITS keyword names and in the
names of table columns (i.e., in the value of TTYPEn keywords).  In
general, hyphens should only be used in cases where there is already a
well defined precedent (e.g., 'DATE-OBS'), or in cases where the hyphen
is specifically used to represent a minus sign.  Otherwise, the
underscore '_' should be used as a punctuation type character to
separate components of the name, (e.g., 'DEC_OBJ' for the keyword
giving the declination of the object).

The purpose of this recommendation is to a) introduce some uniformity
in the keywords used within the OGIP, b) eliminate needless arguments
over which character should be used whenever the names of new keywords
are proposed, and c) reduce confusion by software developers and users
who need to use these keywords.