Re: Community feedback re TAP metadata

From: Iņaki Ortiz de Landaluce <Inaki.Ortiz-at-sciops.esa.int>
Date: Thu, 08 Mar 2007 12:53:23 +0100


Hi there

Please find forwarded our internal view, within the ESAVO Team, on how the metadata access should be handled.

Regarding the open issue about how to perform the queries to such metadata there are two clear and different views: using dedicated query languages (ADQL or SQL) or TAP specific methods/operations. Here we are favor of the second option as we find the query languages a bit too much for such a purpose. We would define a minimum number of simple operations to access the metadata (table, columns and, possibly, the full data model). The ouput of such operations would be in line of what Aurelien is saying in the attached email: reuse the specific elements of the Registry schema, not the full VOResource.

Cheers

Iņaki


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attached mail follows:

Hi Inaki,

Here are my inputs on the subject of TAP metadata access and the relation to Registry schema.
For a start, I believe VOTable is not the "ideal" format for this task, though it could work (just as it worked for SIAP v1.0). It is missing a few elements, and I don't think we should modify an already accepted recommendation for this specific use.
Hence, the output format should be a structured XML, and in this area the Registry WG already did quite some work.... so let's not duplicate efforts. The schema that the Registry WG produced is quite good and would need just a few corrections (missing keys, uTypes, ...). Both WG should work in coordination on this.

Furthermore, I believe like Doug and NVO that a clear separation exists between Service Metadata (that should reside in the Registry) and DataSet Metadata (that should be provided by the service). As Ray, I would not recommend registering the DataSet Metadata in the Registry, though it is possible, but I would certainly discourage providing the Service Metadata by the service itself.

For the query part of the problem, two simple methods should be enough. One to get the description and list of tables, one with a table name as parameter to get the description and list of the columns of that specific table.

Cheers,
Aurelien Received on 2007-03-08Z12:53:40