Issues relating to simple data and metadata queries

[Kona Andrews]

Hi Pat,

> - the difference in opinions on various TAP issues is not all that large 
> conceptually, just lots of details differ

I agree that there are places where our collective opinions on 
the synchronous features of TAP are probably closer than they seem.  

> My thought right now is that TAP is somewhat different from other DAL services 
I also agree that TAP is somewhat different from other DAL services.
In particular, I will shortly post a discussion (by an external author) 
of asynchronous querying for TAP.  This discussion explains very clearly 
why the current DAL model works very well for e.g. SIAP and SSAP, but 
not so well for long-running tabular data queries.  I'm afraid it
is a reasonably long message (sorry!), but that is mostly because it 
takes the time to express itself very clearly and understandably. I do 
hope everyone can at least glance at it.

If, as that discussion suggests, the DAL model is not a good fit for 
asynchronous ADQL querying, I don't think we should be *constrained* to 
make any/every part of TAP concur with the pre-existing DAL protocols 
(however well they work for other kinds of data).  It may be that some 
aspects *do* concur naturally with the existing DAL-based protocols for
other kinds of data, of course; but let's not force the whole thing to 
be a square peg for a round hole.

Cheers,
Kona
-- 
Kona Andrews        kea at roe.ac.uk
AstroGrid Project   http://www.astrogrid.org
IfA, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ