[fitsbits] start of Public Comment Period on the Green Bank convention

[Tom McGlynn (NASA/GSFC Code 660.1)]

It's very unclear to me what the scope of this proposal is.  It is 
unclear how the first two paragraphs relate to the convention since they 
seem to be using the WCS examples where only in the last sentence of 
paragraph 2 do we get to the actual convention.

If the third paragraph of 8.2.1 is normative, then in a table it is 
possible that any keyword is taking the place of a a fixed column in a 
table.  I think this is a perfectly appropriate convention in some 
limited context in which the table columns are
known in some fashion outside of the particular FITS file. However this 
is potentially disastrous as a general convention.  A generic library 
deserializing a FITS file into a table and passing it along to some 
client has no way to know which columns its client is expecting.  The 
only way to deal with this would be to add a column to the table for 
each keyword
in the header.

I believe this convention must remain no more than that unless and until 
some mechanism is proposed to identify the virtual columns.

Note that even as a convention this is not ideal.  When we have table 
columns we not only have a place to put the value we have we can provide 
lots of metadata about the columns: units, logical minimum and maximum 
values, UCDs and so forth.   So even if the identification issue were 
resolved, I'd not be especially comfortable promoting this practice.


        Tom McGlynn



Lucio Chiappetti wrote:
> On Fri, 19 Jun 2015, Lucio Chiappetti wrote:
>
> ANNOUNCEMENT:  START OF FORMAL PUBLIC COMMENT PERIOD
>
> This is to announce the official start of a 3-week formal Public Comment
> Period on the incorporation of the so called Green Bank convention in
> the FITS Standard.
>
> This is part of a process to incorporate the most useful, widely used
> registered, and simple conventions (which are valid FITS constructs) into
> the official definition of the standard.
>
> This convention allows to expand a kewyord in a table column (or collapse
> a column with identical values in a keyword).
>
> The proposed text consists just
>
> - in the ADDITION of a new section 8.2.1 in the WCS section (hilighted in
>    green colour)  describing the usage convention
>
> - in the addition of CROSS REFERENCES to it in 7.2.2 and 7.3.2 after TTYPn
>    (resp.  for ASCII and binary tables), aloso hilighted in colour
>
>     and has been prepared by a technical team including L.Chiappetti,
>     W.Pence, A.Dobrzycki, R.A.Shaw and W.Thompson (main editor
>     W.Pence).
>
> - If the proposal is approved a section H.3 will be added to Appendix H
>    describing the update
>
> The proposed draft text is available at
> http://sax.iasf-milano.inaf.it/~lucio/FITS/Conventions/greenbank-upd2.pdf
>
> Supporting material is provided in the FITS Convention Registry at the
> http://fits.gsfc.nasa.gov/registry/greenbank.html
>
> For general considerations on the Public Comment Period, the IAUFEC review
> and background information on the FITS approval process please refer to
> the announcement of Public Comment Period for CONTINUE issued earilier
> today.
>
> Please review the text carefully and post any comments, criticisms, or
> suggestions on the FITSBITS mailing list, separately for each convention.
> ==================================================================
>
> The Public Comment Period starts today 19 June 2015 and will last formally
> for 3 weeks until July 9 included.
>