[Fwd: Comments on Doug's TAP inputs]

From: Iñaki Ortiz de Landaluce <Inaki.Ortiz-at-sciops.esa.int>
Date: Fri, 20 Apr 2007 16:31:25 +0200

Dear all
Please find attached some feedback from Aurelien Stebe about Doug's inputs on TAP.
Cheers
Inaki

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Hi Pedro,

Here are a few thoughts after reading Doug's TAP inputs. First, there are a few use-cases that I hadn't thought of, and I think there is room for two protocol specifications to cover those use-cases. The "Simple Queries" part describes a TAP sensibly identical to the way I described it, but the "Multiple Catalogs" part is more a description of a <Simple Table Access Protocol>, with a direct transition from "Image" (from SIAP) or "Spectrum" (from SSAP) to "Table" in this protocol.

To make it clearer, I'll define a few words here, the way I understand them at least (which might be wrong, then I'd like to be corrected), because we really need to speak the same language.
- Dataset : a complete entity containing astronomical information of
some sort. This is an Image (in FITS, JPG, PNG, VOTable, ...) for SIAP, a Spectrum (in FITS, CSV, VOTable, ...) for SSAP or even a Table (in FITS, CSV, VOTable, ....) for Doug's "Multiple Catalogs" part of the use-cases.
- Data : some queriable information that is usually (but not always)
saved in a RDBMS. The data for SIAP or SSAP is actually Metadata about Images or Spectra, that is Dataset Metadata. In the case of TAP the data can be absolutely anything, but should be astronomical information about sources.
- Dataset Metadata : for SIAP or SSAP, this is the data. See above.

• Protocol Metadata : the definition of what this particular service can take as input, can return as output in terms of parameter names (POS, TIME, BAND, VERB, ....), table/column names (if supporting ADQL), uType names (if supporting ADQL with uTypes) and default set of fields/columns returned for a DAL-Type simple query. This can be given many names as Table Metadata, Protocol Metadata, Input/Output Metadata, and this needs to be accessible from the service itself (it may be accessible from the Registry also since the XSD permits it).
• Service Metadata : general information and limits of this particular service .... description, curator name, version, URL endpoint, records limit, optional protocol methods support, contact email, .... All this is what the Registry VOResource XSD is here for and it needs to be accessible from the Registry (it may be accessible from the service also, but this is no concern of the specification).

Hence, as I see it, Datasets are accessed using the "getData", whereas Data is queried using the "queryData" operation, the Protocol Metadata is retrieved using the "getCapabilities", or that's what I thought, but it seems it returns Service Metadata (or both ?). The TAP only needs the "getData" and "getCapabilities".

Cheers,
Aurelien Received on 2007-04-20Z16:31:40