m.b.taylor at bristol.ac.uk
Wed Mar 4 01:54:56 PST 2009
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 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/
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