content, format, ctype, or xtype ?

[Doug Tody]

On Wed, 13 May 2009, Arnold Rots wrote:
> MJD is NOT a format!

Arnold said he would scream if any of us made this mistake again;
I think I could hear it all the way here in Socorro.

Seriously though, using UCD would seem to provide a simple solution
without violating anyone's elegant vision and without compromising
UTYPE or UNIT which have more precise usage.  Something simple like
time, time.iso8601, time.mjd, pos.stc might suffice, and the scheme
is easily extensible.

 	- Doug


> Paul Harrison wrote:
>>
>> On 2009-05 -13, at 19:24, Patrick Dowler wrote:
>>
>>> So.... UCD?
>>>
>>> It looks like I object to everything but ucd: it allows one to say
>>> "this is a time". Maybe restriction is enough:
>>>
>>> MJD: DOUBLE <-> datatype="double" ucd="time"
>>> ISO8601: TIMESTAMP <-> datatype="char" ucd="time"
>>> STC-S: REGION or POINT <-> datatype="char" ucd="pos" ?
>>>
>>> Specifically for upload to a TAP service, if the ucd attribute was
>>> missing, the service would put the timstamp values into a VARCHAR
>>> column instead of a TIMESTAMP column. Some things might still work.
>>> If someone replies that there is a suitable UCD fragment for
>>> position (pos?) and energy (?) then maybe we just have to spell this
>>> out (specifically, the table in TAP 0.42, page 19 would be changed
>>> from VOTable:format to VOTable:ucd and we would specify UCD
>>> fragments that signify the content).
>>>
>>> PS-when I say ucd="time" I really mean the ucd attribute contains a
>>> "time" fragment. Can we make this precise enough?
>>>
>>
>>
>>
>> I don't think that this covers all the bases, as there is also the POS
>> expressed as sexagesimal - but running with this idea, what about a
>> set of secondary UCD words format.MJD, format. ISO8601, format.STC,
>> format.hms, format.dms to be added to time.epoch etc.
>>
>>
>> Paul
> --------------------------------------------------------------------------
> Arnold H. Rots                                Chandra X-ray Science Center
> Smithsonian Astrophysical Observatory                tel:  +1 617 496 7701
> 60 Garden Street, MS 67                              fax:  +1 617 495 7356
> Cambridge, MA 02138                             arots at head.cfa.harvard.edu
> USA                                     http://hea-www.harvard.edu/~arots/
> --------------------------------------------------------------------------
>