On Thu, 20 Apr 2006, Thomas McGlynn wrote:
> While Roy and Dave may have hinted at this, let me say very
> plainly that I think this is a bad idea. Coordinates in
> VOTables should be respresented in decimal degrees and
> any other usage should be strongly discouraged. Allowing
> other formats makes the job of software which is to
> read and write VOTables much harder and more error prone.
That's a reasonable point of view; I think I've given my response to it in my previous message about pragmatism. I'd add though that I don't recall it ever being recommended (e.g. in the VOTable document) that putting sexagesimal in VOTables is bad practice, and it doesn't seem obvious to me that it's worse practice in VOTables than in FITS and various ASCII format tables, and there's certainly a lot of those that do it.
> User interfaces must support sexagesimal coordinates
> but they will need to be able to convert between
> decimal values and sexagesimal formats in any case so
> there is no savings there. The number of sexagesimal
> formats used in the community is large
> hh mm, hh mm.f, hh mm ss, hh:mm, hhHmm, hhHmm.f, hh:mm, ...
> and this brings up a whole issue of validation of the
> units. I.e., XML can validate that a number is a number
> but unless we do a lot of work it's going to be hard to
> validate XML documents that claim to have sexagesimal
> coordinates.
There's a salient point in there, but validation is a red herring. XML validation of a VOTable does *not* validate anything about table cell contents, such as whether it's a valid number or not. XML schema doesn't know nearly enough about VOTable document structure to do this, only a parser which understands the VOTable format can do that. Similarly,
> P.S., for times there is an ISO standard and we should allow that.
> That may be supported in the XML standard but I cannot recall if that's
> true.
yes XML schema does understand ISO-8601 but no VOTable isn't designed in such a way that it can make any use of that fact.
Mark
-- Mark Taylor Astronomical Programmer Physics, Bristol University, UK m.b.taylor@bris.ac.uk +44-117-928-8776 http://www.star.bris.ac.uk/~mbt/Received on 2006-04-20Z20:25:56