STC in VOTable: Time utypes

[Markus Demleitner]

Dear VOTable and DM folks,

On the issue of a common container I've received only positive
feedback, so I'll go ahead and have the next draft include that.

Meanwhile, another issue has come up that I'd like to hear opinions
on: The time utypes.  Currently, they look like this:

stc:AstroCoords.Time.TimeInstant.ISOTime or
stc:AstroCoords.Time.TimeInstant.JDTime.

I've just put the following diatribe on this on the wiki page
(http://www.ivoa.net/cgi-bin/twiki/bin/view/IVOA/STCInVOTable):

"""
That is bad for at least three reasons:

   1. clients have a hard time figuring out what column a time or a time 
      error or whatever is (since they need to check at least three utypes)
   2. we have xtype in VOTable for this purpose, and having both utype 
      and xtype specify something then requires some rules on what to 
      do when the attribute contradict or if there is some inference 
      between them
   3. data models should IMHO not be concernded with serializations

So -- what's to be done?

   1. Keep everything as is (ugly, but probably workable; declare 
      clashes between utype and xtype as undefined)
   2. Elide ISO/JD/MJDTime by special rule (but that's yet another 
      special rule, and you cannot build an STC-X tree from utypes any more)
   3. Change STC-X (would probably take a while and might be used 
      to clean up some other ugly spots we have here, but it's a
      major undertaking that would seriously delay STC-in-VOTable)
   4. ???
"""

(at the very bottom).  Emboldend by the feedback to my last question,
I thought I'd ask around again for opinions and suggestions --
preferably on the wiki.

Thanks,

          Markus