HFWG Recommendation R6:

     On the minimum and maximum actual and legal values within
                   columns of FITS tables

                    (Approved: 1993 Aug 27)


If it is necessary to use keywords to store the minimum and maximum
values contained within column n of a FITS table, the following
keywords should be used:

	TDMINn
	TDMAXn

respectively. These keywords are directly analogous to the DATAMIN and
DATAMAX keywords used in association with the primary array and have
been adopted elsewhere within the FITS community.

If it is necessary to use keywords to store the minimum and maximum
legal values that may be stored within the elements of column n of a
FITS table, the following keywords should be used:

	TLMINn
	TLMAXn

respectively. The following recommentions are also made for clarity:

- The datatype of the keywords should be the same as that of the table
column (n) to which they refer.

- The keywords refer to <all elements of a vector column.

- These keywords impose no constraints or information regarding the
meaning of any null data values within the data.

- The values of the keywords should be such that they should be
compared to the data values stored in the column after those data
values have been multiplied by/added to the values stored in the
corresponding TSCALn and TZEROn keywords.

- It should not be forbidden to have values of TDMINn less than TLMINn
or TDMAXn greater than TLMAXn, leaving it to individual applications as
to what such situations imply.

- If the keyword for the minimum value be <b>greater</b> than that for
the maximum value (i.e. TDMINn is greater than TDMAXn or TLMINn is
greater than TLMAXn as appropriate), then this should be taken to mean
that the values had not been defined.