SIA Evolution proposal
Alberto.Micol at eso.org
Thu Apr 15 04:27:42 PDT 2004
Just a very brief summary, a question to Pedro and Jesus (VILSPA),
and, for "par condicio", a question to Thomas, Francois and Mireille (CDS),
on the SIA evolution proposals:
Both proposals manifest the same requirement: the need
to provide enhanced metadata to a user of a S?A service (being it a SIA,
The different is in the implementation, whereby:
- VILSPA uses VOTable "nested tables"
- CDS, which used VOTable "nested resources" in a previous version,
in the last proposal simply uses a second GeneralFeatures resource
parallel to the "main" resource (the one containing the S?A results).
Such resource contains as many tables as needed to describe properties
that otherwise would get repeated (eg filter descriptions, telescope
Very much like one would design his/her relational database.
NOTE: In the CDS document that processed is labeled "factorisation",
which is probably coming from some french translation, I would call
(from the relational word), but I'm italian ...
The VILSPA proposal will require a modification of the VOTable schema
to allow TABLE as a possible datatype for a FIELD element.
CDS does not require any change, and indeed is already used by various
What is not clear to me, in the VILSPA proposal, how to avoid
The example by Pedro and Jesus shows a single record; but suppose that
(say 4) are returned, and suppose that 2 observations were taken in
energy band A and
2 observations were taken in energy band B. The same Energy_Band_Table
seen in two different records for both the A filter and the B cases.
In the CDS case that is done by putting all the Energy_Band (filter in
the cds case) definitions
into a single filter table in the GeneralFeatures resource, and by
referring to it.
(btw, the link should not be done on the filtername, but on a filter
since the same filter name could be used by two different instruments
(see F555W for
both WFPC2 and ACS)).
Pedro or Jesus, could you please clarify that?
What is also not clear is how, with the new proposed CDS structure, one
could describe multiple members of observations. In the previous IDHA
that was achieved with "nested resources"; but now?
Francois et al., could you please clarify that?
A side comment more for the VOTable WG:
I like the capability of nesting tables; that would allow a one to one
some special FITS file and VOTable. The HST/STIS extracted spectra are
in nested tables (a table cell contains a spectrum) indeed!
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