Elements to add to TabularSkyService

[Martin Hill]

Roy Williams wrote:

> Why is this schema being rebuilt? 

It's not really; this is an existing one that has been around for a while.

> The PARAM in VOTable is semantically IDENTICAL to this new thing. Isn't it?

Sort of but not really; there are some shared attributes because the VOTable 
header is doing a similar thing: describing the characteristics of a column of 
data.

However the VOTable header element has some rather peculiar aspects (see I *can* 
be nice about it :-) to do with it's age (PARAM?!) and the way data is stored in 
VOTables (array of chars?) that are not really suitable for what we want to do 
with the metadata just now. Nor is it trivial to extract PARAM from VOTable. 
Nor is it easy to introduce changes to the VOTable format; the concept of 
<ErrorColumn> has been turned down before, and we need that!  I suspect (though 
this is a different thread) we will also need versioned UCDs for the metadata, 
so that both older and newer clients can use datacenters.

If we find they converge later, then it might be worth the effort of extracting 
PARAM to its own schema and reusing it.

In fact, although I suspect VOTable advocates will recoil at the thought, it 
will be far more useful to remove the VOTable header and replace it with a 
suitable VOResource extension (when they are ready), so that the data in the 
table can be more fully described....

Cheers

Martin

-- 
Martin Hill
www.mchill.net
+44 7901 55 24 66