PR-TAP-1.1 - Some comments

Mark Taylor m.b.taylor at
Fri Sep 8 13:44:23 CEST 2017

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
> 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.
> Anyone in for writing an Erratum?
> > On Wed, 19 Jul 2017, Mark Taylor wrote:
> > 
> > >     In general I think all of the TAP_SCHEMA table columns
> > >     defined in sections 4.1-4.4 should be described using the
> > >     generic terms either "integer" or "string" (or "character array").
> > >     Mandating VOTable datatype and arraysize attributes looks
> > >     to me like introducing more problems than it solves.
> > 
> > I think that listing the VOTable-specific attributes datatype,
> > arraysize and xtype in these tables is unnecessarily confusing.
> Just to be sure: by "these tables" you do not refer to the TAP_SCHEMA
> tables themselves but to the tables in the spec?  If so, then I

Yes, I'm talking about the tabulated descriptions in sections
4.1-4.4 prescribing the content of the TAP_SCHEMA, er, tables.

> agree; let's boild them down to "integer" and "string" (and perhaps
> mention that "string" includes what in VOTable would be an array of
> unicodeChars; in particular descriptions should be allowed to contain
> ødd chåräçtérs

Agreed, "string" and "integer" are intended to permit any suitable
string-like or integer-like types at the implementor's discretion.

Mark Taylor   Astronomical Programmer   Physics, Bristol University, UK
m.b.taylor at +44-117-9288776

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