[fitsbits] The CONTINUE and HIERARCH Conventions Public CommentPeriods

The description of the HIERARCH convention is inconsistent, I think,
regarding the length of the component tokens.

At the top of p. 2 it says

"Under the ESO implementation of this convention, each token string which
precede[s] the equals sign conforms to the requirements for a FITS
keyword..."

But in Section 2, this rule is abandoned and the same scheme is used for
defining long and non-conforming keyword names. So, as written it is not
really clear whether it is the ESO implementation that is being discussed,
or the more general thing. That is, would the following conform to the
convention?

HIERARCH HST-ADVANCED-CAMERA APERTURE$Setting = 2

Finally, on p. 3 it says "This convention should not be used if the
effective keyword name can be represented as a standard FITS keyword...". I
think it can be argued that one can always find a standard FITS keyword
representation, as has been done 1000s of times in FITS headers. The
examples given, such as ESO.TEL.FOCU.SCALE and ESO.INS.OPTI-3.ID, would have
quite obvious standard keyword values given the context of a FITS file
originating from an ESO telescope and instrument, which would be documented
elsewhere in the FITS header.

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 have regretted it at various times ever since.

Bob


On 9/6/07 12:34 PM, "William Pence" wrote:

First, a reminder that the Public Comment Period on the CONTINUE keyword
convention will be closing soon.

Second, the Public Comment Period on the the ESO HIERARCH keyword
convention is now open.

Detailed information about both of these conventions is available for
public review and comment from the FITS registry web page at

http://fits.gsfc.nasa.gov/fits_registry.html

Comments about these conventions may be posted here on the FITSBITS mail
exploder or the sci.astro.fits newsgroup. Minor typographical issues
may be sent directly to the authors of the convention.

Bill Pence
(on behalf of the IAU FITS Working Group)

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Brief description of the HIERARCH keyword convention:

Under the HIERARCH keyword convention, as originally defined by ESO,
bytes 10 through 80 of the HIERARCH keyword record contain a series of
ASCII strings, or tokens, that serve to hierarchically classify the
keyword, followed by an equals sign ('=') which is in turn followed by
the keyword value field. An optional comment field may follow the value
field. The value and comment fields conform to the rules for free-format
keywords, as defined in the FITS Standard document.

The following is an example of this convention:

HIERARCH ESO INS OPTI-3 ID = 'ESO#427' / Optical element identifier

The hierarchical keywords can be mapped into variable names by
concatenating the hierarchical tokens together, separating them with the
full stop character. For example, the hierarchical keyword shown above
corresponds to the variable name ESO.INS.OPTI-3.ID.

This ESO convention can be generalized to support keyword names longer
than 8 characters, or which contain ASCII characters that would
otherwise be prohibited. Some examples are shown below:

HIERARCH LongKeyword = 47.5 / keyword has 8 characters and mixed case
HIERARCH XTE$TEMP = 98.6 / This keyword name contains the '$' character