Support for data containing NaN values

[Mark Taylor]

Mike,

in fact VOTable does permit NaN values in (single or double) floating 
point data; I think this is a consequence of the design decision
that the VOTable model for data is to be as close as possible to
that of FITS.  Furthermore, NaN is how VOTable recommends to represent
NULL values in floating point data (again, following FITS) - whether
that's a good idea or not is a question that has been debated elsewhere,
but that's what VOTable section 6 says 
(http://www.ivoa.net/Documents/VOTable/20091130/REC-VOTable-1.2.html#ToC41)

Mark

On Mon, 26 Sep 2011, Mike Fitzpatrick wrote:

> I took the question differently:  If VO allows FITS  data, and
> FITS data allows NaN, then apps should of course allow
> for this.  OTOH, if the question is whether "VO data" as is
> serialized in a VOTable allows NaN values the I think the
> answer is 'no' (but I'd have to check).  There are similar issues
> with how NULL values are handled, but again it depends on
> whether it is in the serialized VOTable or the end data product
> being accessed.  The DAL protocols don't say anything about
> NaN/NULL beyond how they might be serialized, FITS is FITS
> and if that's what the app retrieves in the end and then that is
> the standard to follow when interpreting the data.  Was that
> your question?
> 
> My $0.02,
> -Mike
> 
> 
> 
> On Mon, Sep 26, 2011 at 2:06 AM, Mark Taylor <m.b.taylor at bristol.ac.uk>wrote:
> 
> > On Thu, 22 Sep 2011, Randy Thompson wrote:
> >
> > > As a general question, does data containing NaN values
> > > violate any VO standards or protocols,and if not, should VO
> > > applications be expected to accept them as input?
> >
> > the question is rather broad ("data" can take many forms), but on
> > the whole the answer is that most standards and software in the VO
> > should and do behave sensibly in the presence of NaN-valued floating
> > point values.
> >
> > --
> > 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/
> >
> 

--
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/