STC-S WD

[Norman Gray]

Markus, hello.

On 2012 Jun 6, at 03:46, Markus Demleitner wrote:

> (1) There should be a proper BNF grammar for STC-S.  I have one at
> http://docs.g-vo.org/stcsgrammar.txt, which is machine-generated and
> thus quite ugly, but it should be pretty much what Arnold intended
> (with the exception of the velocity subphrase, which needs fixing in
> that grammar).  With a bit of sympathetic attention, it should be
> rather straightforward to turn it into something actually readable.

I'd like to suggest making a yacc-style grammar instead, on the grounds that there's a broader range of tools which can read yacc-style grammars, than can read BNF.

If I recall correctly, Yacc-style syntax is essentially equivalent to BNF, with the only (significant) difference being that there are more parser generators which can read the yacc-style variant of the syntax than can read BNF.

I've some experience with Yacc, Bison, and friends, so I can help here if necessary.

> (2) I think the preterminals in the BNF grammar should be linked to
> the actual data model via utypes generated according to the recipe in
> the STC-in-VOTable note,
> http://www.ivoa.net/Documents/Notes/VOTableSTC/, mainly for reasons
> of conceptual hygiene.  The downside of this is that these utypes are
> generated via the STC-X schema, which is regarded by many, including
> me, as suboptimal.  However, it seems there is no significant
> initiative to come up with a better formalization of the STC data
> model (or is there?), so I feel it's the best we can do.

For another project, I'm currently working on making an OWL version of the STC model, starting from the STC model document, and with help from Arnold.  This may or may not produce a better way of writing these utypes.

All the best,

Norman


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