PR-TAP-1.1 - Some comments

Patrick Dowler pdowler.cadc at
Mon Sep 11 21:13:26 CEST 2017

So just to be clear: the interpretation of arraysize="1" vs null (in
tap_schema) or missing (in a VOtable) isn't just cosmetic because
null/missing means a scalar and 1 means an array?

I never thought about that detail much and I guess assumed it was more
like the database treatment than the resulting datatype (int vs int[])
in software.


On 8 September 2017 at 05:01, Mark Taylor <m.b.taylor at> wrote:
> On Fri, 8 Sep 2017, Markus Demleitner wrote:
>> Dear DAL,
>> On Fri, Sep 08, 2017 at 11:42:49AM +0100, Mark Taylor wrote:
>> > I always thought that in VOTable (following FITS practice),
>> > setting the arraysize attribute to "1" has an identical meaning
>> > to omitting it, i.e. that VOTable makes no distinction between
>> > a scalar and a single-element array.  However now that I look
>> > I can't find that confirmed (or denied) in the VOTable specification.
>> Hmha -- I think the fact that TOPCAT/stilts and astropy, certainly
> [I didn't realise astropy did that differently]
>> among the two most widespread consumers of VOTables out there,
>> disagree on that point is a strong indication that we need to clean
>> this up.
> ... but it also means that cleaning it up would be pretty difficult
> to do.  If we decree that one or the other interpretation is correct,
> it means one or the other popular software item ought to change its
> behaviour in a probably backwardly-incompatible way.
>> Anyone in for writing an Erratum?
> So, no, since I don't know what it would say.
> --
> Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
> m.b.taylor at +44-117-9288776

Patrick Dowler
Canadian Astronomy Data Centre
Victoria, BC, Canada

More information about the dal mailing list