[TIMESTAMP] Re: TAP1.0 Comments

[Mark Taylor]

On Mon, 20 Jul 2009, Patrick Dowler wrote:

> On Monday 13 July 2009 09:34:30 Francois Ochsenbein wrote:
> > 2.3.4 (and other places where ISO8601 is quoted):
> >      as far as I know, this norm requires the 'T' in front of the
> >      time; the timestamp format should therefore be written
> >      "yyyy-MM-dd[Thh:mm:ss[.sss]]" (the 'T' is missing in the document)
> 
> A while back we asked around and some RDBMSs do not like the format with the T 
> in the middle, while all respondents indicated that the one with a space 
> between date and time could be parsed. The T was dropped from the document so 
> that timestamp expressions would not have to be parsed and converted (by as 
> many people, anyway). 
> 
> If we use the format with T, then more services will have to find, parse, and 
> re-write timestamp literal values. This is primarily an issue for ADQL, where 
> there is already plenty of whitespace and queries have to be encoded for 
> transport anyway... 
> 
> Thoughts?

Francois is correct that the 'T' separator is part of the ISO-8601 
standard.  However, ISO 8601:2004(E) contains the following note:

   "NOTE  By mutual agreement of the partners in information interchange,
    the character [T] may be omitted in applications where there is no 
    risk of confusing a date and time of day representation with 
    others defined in this International Standard."

so I think the DAL authors are at liberty to decide whether the T is 
to be used in this context, without being in danger of violating the 
ISO 8601 standard.  From what Pat says, pragmatic considerations 
would seem to indicate omitting it, so I'd say that was probably 
the thing to do.

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/