It isn't really all that dire :)
The crux is that to use TAP the user needs to know the table name unambiguously; in the db this is the fully qualified table name (FQTN for short), which is $catalog.$schema.$table
For the purposes of TAP 1.0, it would be sufficient to say that the VOResource metadata about tables an columns (which is what one needs for discovery anyway) has to specify unique, unambiguous table names.
What we should be careful about is to make sure that we do not include any semantic meaning in such FQTNs - just say they have to be unique within the service and leave it at that. In MySQL there is one catalog, so FQTNs can be reduced to $schema.$table in that case. In general one always has a default catalog they are connected to, so any TAP service which keeps all the content in one catalog could do the same... others that expose multiple catalogs via a single TAP (eg upload VOTables to a VOSpace and they are available in the service) might want to do that or they might want to use a separate catalog; that is defintely what I would do. Still others might have historically used the catalog as the namespace (we do that in our sybase servers, eg), so there we would use FQTNs like $catalog..$table or $catalog.dbo.$table.
Summary: I think we could get away with just having 1+ opaque unique table names in the VOResource metadata and TAP implementors can decide if they want to put something arbitrary and map it to their DB or they can just put their real FQTN in there and not have to process the ADQL at all. We just have to make sure this thing has no specific meaning (well, people will see and parse it and make assumptions anyway, that's unavoidable) that ties us down later.
my 2c,
Pat
On 2007-10-12 01:08, Tony Linde wrote:
> I thought TAP was a mechanism for sending ADQL through to registered
> services. The various posts here sound like trying to solve perceived
> problems with ADQL and Registry in TAP: that IMHO is the wrong way round.
> TAP spec should simply be used to push ADQL to a service then you get the
> changes you want into ADQL and the Registry and TAP still works. If ADQL is
> changed so that it supports qualified table names then, and only then,
> should you update TAP to support the new spec, not try to predict what ADQL
> might look like in the future. If OTOH you are saying no-one can possibly
> use ADQL as it stands and there is no point producing TAP based on the
> current ADQL spec then you should get ADQL changed first, but I really do
> not think that is the case.
-- Patrick Dowler Tel/Tél: (250) 363-6914 | fax/télécopieur: (250) 363-0045 Canadian Astronomy Data Centre | Centre canadien de donnees astronomiques National Research Council Canada | Conseil national de recherches Canada Government of Canada | Gouvernement du Canada 5071 West Saanich Road | 5071, chemin West Saanich Victoria, BC | Victoria (C.-B.)Received on 2007-10-12Z19:01:27