Time/Target mandatory

[Petr Skoda]

Just following when time permits ...


> On the other hand, I think we'd be doing ourselves a favour if we
> outlawed NULLs in mandatory fields and only made items mandatory for
> which we're confident we're not blocking use cases we'd like to cover.

I must say that  current SSA services has  NULLs in mandatory 
fields as the information is either unknown or some "artificial" whould be 
needed - so its better to leave the data importer to keep the NULL.
(mostly spatial bounds - angular diameter depend on slit width - it may 
not be recoderd in FITS if it is manually controlled....)


and still there is a problem with mandatory DataSet.Length - when using 
postprocessing in WCS (angstroms) - its not sure what to put in query 
result - the length depends on postprocessing done and this happens after 
the vot with results is created.

so the number of points is a bad example for mandatory parameter ...


>>> or yet something else -- or maybe drop the requirement for
>>> Target.Name entirely?  What, by the way, is the rationale for having
>>> it mandatory?

Target name in SSA1 is not mandatory and it has fatal consequences.
The server is not obliged to understand it so it ignores it.

So when you query using TARGETNAME for particular object - even for your 
well-known data (you are sure this name is in FITS header)
you do not get selection done and all spectra are returned from some 
servers..


>> I don't think it ever needs to be empty, because it is certainly a spectrum
>> of something.

no suppose you are searching for something. IT MUST have some name.

But what is in IVOA aproach against the common sense of astronomers - is 
the wildcard search - it should be definitively solved and legalized 
(Markus has a hack called WILDTARGET in DaCHS)


> Ah, I disagree on the "intended for query".  SSAP has always allowed
> searching by target name, although it's hard doing this in a useful
> way just now (essentially, we're missing a reliable way of
> discovering object names available).  In Planetary Sciences,
> searching by target name is yet more important.

DEFINITELY

there is sometimes no other way how to query for certain spectrum
e.g. if you have two stars from double star on slit - all the processing 
pipeline will assign the coordinates of the telescope during observation - 
identical.

How you distinguish only one particular star if cone search always returns 
two of them ?

I must use very often SSA query TARGETNAME=

> prescription for the domains or serialisations.  And object "object
> name" and "unique" just don't go together, I'm afraid.

Everything in science is unique - the troubles stems from our disability 
do agree on common  naming scheme.

But in general various schemas are used by astronomers.
So let them decide what they expect to get ...

simple wild target search is necessary !

here the 80/20 rule applies as well.

--------------------------------------


Another important practical aspect - where should we put the observer's 
name in SSA model ?
Its definitively the most important for the success of VO data publishing
publisher etc is not what the people want - they want to see automatically 
in VO credits for their effort either as a PI , observer and "data 
reducer"

On every observatory I have seen is this written in FITS headers and we 
need to keep it as integral part of every spectrum.

It may be different for surveys, anyway

Petr Skoda