VOTable 1.2

[Mark Taylor]

Hi Francois,

On Tue, 3 Mar 2009, Francois Ochsenbein wrote:

> >  On Tue, 3 Mar 2009, Mark Taylor wrote:
> >>
> >> >   1. Why change INFO syntax at all?  There may be good reasons,
> >> >      but I don't recall this proposal, or the motivation for it,
> >> >      being discussed on the VOTable list.
> >>
> >> ==> That was the result if a discussion in an IVOA meeting,
> >>     effectively not discussed on the mailing list
> >
> >I see.  This doesn't answer my question - what was the motivation?
> >
> ==> If I remember correctly, the motivation was to enable possible
>     extensions -- a tag containing a simple text can't be
>     extended if necessary. You are right this should be discussed
>     a bit more -- Doug would certainly agree with you :-)

Sorry, you'll have to explain that a bit more, I don't understand
what sort of extension you are talking about.

> >In any case, I would like to request that in future such changes are
> >discussed, or at least presented, on the mailing list.  Even for
> >interested parties who attend IVOA Interops, they may be unable
> >to attend VOTable sessions.  Airing such issues on the mailing list
> >both gives all interested parties a chance to contribute, and
> >provides a record of any views which were expressed.
> >
> >> >   2. If INFO is only for strings, why does it have a 'unit' attribute?
> >>
> >> ===> Being made similar to PARAM, there is no reason to forbid the
> >>      unit attribute -- after all strings may also represent things
> >>      with attached units, like time intervals.
> >
> >Please give an example.  If you're talking about ISO-8601 strings,
> >I don't think a unit is appropriate, since the units information such
> >as it is is implicit in the format.
> >
> ===> Well a time difference (duration) does not need to be 
>      expressed in ISO format -- might be days and hours for instance.
>      Another example could be a region on the sky,
>      does not need to be expressed in degrees either.

what are you saying, 

   <INFO value="three" unit="days"/> ?
   <INFO value="3 6" unit="days and hours"/> ?

Please give me an example of an actual usage of INFO (element
content and attributes, as above) which uses a string value and 
the unit attribute to sensible effect, rather than vague references
to the issues.

> >> ===> same as 2. above -- could be useful
> >>
> >> Do these modifications prepresent problems for STILTS ?
> >
> >Not insuperable problems, but changes in the syntax of an element
> >between different VOTable versions complicates the implementation.
> >If there is some good reason for the change, I don't mind making the
> >additional effort.  But if it just seemed like a nice idea to the
> >handful of people at a VOTable session a few interops ago and
> >nobody can remember why, I'm not so enthusiastic.
> >
> ===> The change in Aladin was really lightweight -- skip the
>      <DESCRIPTION> tag. But again you are right for the
>      necessity of discussion -- on the other hand during
>      the discussion it looked as a good simplification.

If it is a good simplification, then it may well be worthwhile.
But I haven't seen the discussion.

Mark

-- 
Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at bris.ac.uk +44-117-928-8776 http://www.star.bris.ac.uk/~mbt/