[Semantics] Re: UCDs and arrays : histogram case

[Markus Demleitner]

Hi Mireille,

On Sun, May 20, 2018 at 10:15:47PM +0200, Mireille Louys wrote:
> I did not succeed in visualising the table example you mentionned . I there
> a special way to find it  via taphandle , and or topcat?

Just enter the TAP service URL (or select "GAVO DC TAP" from the
given list of services) in your client and execute the query
-- did this not work for you?

> for the choice of the ucd label, I vote for "stat.histogram" , but I suppose
> it makes sense to bind it to the measure it has been collecting .

Certainly stat.histogram would need to admit declaring what has been
aggregated.  However, I'm pretty sure stat.histogram still needs to
be P.  Consider the existing term stat.error, which is P because an
<error of X> is *not* somehow a subclass of <X> (contrary to, say,
stat.max, which consequently already is Q).

Analogously, a <histogram of X> is a different beast from <X>, and
clients that, for instance, cut off trailing atoms to figure out
roughly what something is would be completely mislead.

So, in the example, the UCD of the dist column should be

stat.histogram;phot.mag.V

(it's not yet, but based on your feedback I'll put it in soon as a
prototype).

       -- Markus