VOUnits RFC

[Norman Gray]

Rick, hello.

On 2013 Jul 29, at 17:56, Frederic V. Hessman wrote:

> I would also like to see a more formalized grammar in the document, also pointing in future directions, rather than the collage of previous and future standards (with lots of empty table boxes).   This is what a real VO programmer is going to need and the grammer might even be useful as input to some grammar parser (I used to understand yacc grammars, but it's been decades, so please excuse my non-formal syntax).   Just having a bunch of tables is ok, but it's hard to distill a standard from them.

The grammars are collected in Appendix C (I see the actual tables 16--19 have drifted to the end of the document, but that's a LaTeX issue I can fix up).

The tables you're referring to (in Appendix B?) are there just for more-or-less historical reasons, to try to highlight the variations between syntaxes, and so imply the motivation for this Recommendation (ie, the current practice is so very heterogeneous as to be regarded as a Mess).  I'll add some text at the beginning of this appendix to make this clearer.

The grammars are also available at <http://www.astro.gla.ac.uk/users/norman/ivoa/unity/grammar/>, and the Unity library <http://www.astro.gla.ac.uk/users/norman/ivoa/unity/> is implemented using parsers generated from these grammars, which confirms that they're consistent.  See also test-cases in the .../grammar/ directory.

All the best,

Norman


-- 
Norman Gray  :  http://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK