New RFC (Was: VOUnits: _another_ version, based on implementation feedback)

[Arnold Rots]

Two comments:

One could allow, without stating case-insensitivity, two strings
to indicate unknown units: "unknown" and "UNKNOWN".

What is one to do if one wants to provide VO-compliant metadata
for a FITS file that contains (regrettably) time-related items expressed
in units of ta or Ba?

Cheers and happy Boxing Day,

  - Arnold

-------------------------------------------------------------------------------------------------------------
Arnold H. Rots                                          Chandra X-ray
Science Center
Smithsonian Astrophysical Observatory                   tel:  +1 617 496
7701
60 Garden Street, MS 67                                      fax:  +1 617
495 7356
Cambridge, MA 02138
arots at cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
--------------------------------------------------------------------------------------------------------------



On Tue, Dec 24, 2013 at 2:33 PM, Norman Gray <norman at astro.gla.ac.uk> wrote:

>
> Dear all,
>
> On 2013 Nov 6, at 11:25, Norman Gray <norman at astro.gla.ac.uk> wrote:
>
> > The DocStd document <http://www.ivoa.net/documents/DocStd/> says (Sect.
> 2.2) that "Such revisions must be minor in nature, or else the document
> must return to Working Draft status."  Perhaps the formally correct thing
> to do, therefore, is reissue this as a WD and put it immediately into RFC.
>  I hope that most people who would comment on that would have now commented
> in the post-TCG phase, so I imagine that this RFC would be quiet, and the
> document could then be immediately and automatically promoted to PR and
> thus TCG review.
>
> I have (finally!) updated the document, and the associated grammars, to
> match the discussion on-list (or at least I think I have -- please check).
>
> Mireille created a new RFC page (thanks, Mireille!), which is pointed to
> in the text below, just above my signature.
>
> I've uploaded the document to the IVOA document registry but, given the
> date, I doubt this can, or indeed should, be attended to before the New
> Year.
>
> I've suggested an end-date of 2014 January 31 for the RFC.
>
> Thanks, everyone, for your patience.  We're on the home stretch now.
>
> Very best wishes,
>
> Norman
> [shutdown -h +10]
>
> ----
>
> A few comments on the changes I've made:
>
> I've unilaterally added 'au' as a permissible alternative to AU, because it
> seems perverse to prefer atto-atomic-units to astronomical units.
>
> I've deleted the reference to \unit{Sun}, because there's been no
> discussion of
> how to actually use this, and it's not obvious what the syntax should
> be; it's not supported in the Unity library.
>
> The Bessellian and Tropical years ('Ba' and 'ta') remain as FITS
> units, but they remain 'unknown units' within the VOUnits spec.
>
> The text now states more prominently that `unknown' (lower-case) is
> the single indication that a column has unknown units, and that an
> empty string positively indicates that a column is dimensionless.
> Both must be checked for before unit-parsing starts, since both
> produce invalid unit-strings.  My reservations about these two points are:
>
>   * I don't like case insensitivity (agreeing with Markus), but there
>     seems a case for it here, since I can imagine someone trying to
>     remember whether the magic string was "unknown" or "UNKNOWN",
>     remembering the wrong way, and ending up with a correctly
>     parseable (though unknown) unit called the 'UNKNOWN'.
>
>   * The problem with an empty 'dimensionless' string is that it's not
>     clear that someone has deliberately stated "this quantity is
>     dimensionless", as opposed to "I forgot to put in the units", or
>     "I couldn't be bothered", or "I don't know what the units are and
>     didn't know I was supposed to write 'unknown'", all of which are
>     plausible interpretations of "", if one were to find it in a file.
>
>
>
> ----
> This is part of a discussion of "Units in the VO"
> IVOA Proposed Recommendation 1.0-20131224
> Editor(s): Sébastien Derrière and Norman Gray
>
> PDF:
> http://wiki.ivoa.net/internal/IVOA/Dec2013VOUnitsRFC/PR-VOUnits-1.0-20131224.pdf
> changes:
> https://code.google.com/p/volute/source/browse/trunk/projects/std-vounits/VOUnits.tex
> changes: https://bitbucket.org/nxg/unity/commits/all
> RFC: http://wiki.ivoa.net/twiki/bin/view/IVOA/Dec2013VOUnitsRFC
>
> --
> Norman Gray  :  http://nxg.me.uk
> SUPA School of Physics and Astronomy, University of Glasgow, UK
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.ivoa.net/pipermail/semantics/attachments/20131226/f37c3562/attachment.html>