DALI 1.1 working draft available

[Arnold Rots]

UTC may be a DALI restriction, but time zones are specifically outlawed,
both in FITS and in STC.
On an earlier comment, decimal years can simply be specified with unit='a';
but they would require an indication 'B' or 'J'.

  - Arnold

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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 cfa.harvard.edu
USA
http://hea-www.harvard.edu/~arots/
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On Fri, Feb 19, 2016 at 12:30 PM, Patrick Dowler <pdowler.cadc at gmail.com>
wrote:

> As has been discussed numerous times (!) in the past, JD and MJD are *not*
> types. For MJD values (eg Obscore t_min and t_max) one uses
> datatype="double" unit="d" and describes the coordinate system metadata
> using STC as Markus has described in a Note. The xtype attribute is to tell
> consumers of the votable that the value can be further parsed to turn it
> into a structure of some type, not further interpretted to mean something.
> I think that is an important distinction that is often ignored
>
> I'm not sure about the high precision "days" + "seconds" double array. You
> need that in TAP only if you actually want to expose a single column with
> the multiple values, but I don't know off hand if anyone does that. (I will
> admit to having some double array vaulued columns in our TAP service; they
> are in a view called caom2.SIAv1 to support the coupleof columns in the
> SIAv1 output that are arrays... but they don't have xtypes).
>
> Finally, the restriction of timestamps to a specific ISO8601 in UTC and
> without timezone comes from upstream of DALI -- VOResource iirc. It has
> been th accepted standard for years and DALI is only formalising some
> technical bit of it for usage in services like TAP, SIA2, etc
>
> Emphasis: xtype tells the consumer how to further parse the value.
>
>
> --
> Patrick Dowler
> Canadian Astronomy Data Centre
> Victoria, BC, Canada
>
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