Registries, IVO ids, and Data Set Identifiers

[Alberto Micol]

Robert Hanisch wrote:


> Alberto M. would argue against using instrument names, as in some sense they are redundant for HST observations.  This may not be true for other missions, projects, or telescopes.

If that is not true, than the instrument name should be part of the dataset ID
and, hence, be on the right side of the '#' or '?' symbol, not on the left !

But most importantly:

> ...
>
> Having separate authority and resource components allows

> o  Different providers of the "same" data to offer enhanced data products,
> and authors to be clear about which they are citing.

That's important! But remains the problem of two identical datasets
offered by, say, MAST and STECF. In that case, how would one know
that the two identifiers

ivo://hst/mast.acs#q1234567.fits

ivo://hst/stecf#q1234567.fits

are to be considered IDENTICAL ?
(btw the .fits extension indicates a file, not a dataset)

Is not that what the dataset ID is for ? to uniquely identify a dataset ?

Would:

ivo://hst/stecf?set=q1234567&identical_to=ivo://hst/mast.acs#q1234567

help here ?


/*
For the non-HST persons in this forum:
In the STScI/CADC/STECF case, the same dataset ID could refer
to three (a) equal, (b) slightly different, or (c) very different products!
And that could be for various reasons ... STECF and CADC cannot
*always* be considered mirror sites of the HST archive ...
*/

And, yes Bob, the authors will have to use the right one, that is, that MAST
one if the data where retrieved from STScI, the STECF or the CADC or the NAOJ
one in the other cases.
(How will the STScI person in charge of cross-correlating publications and program ids react to this ? Is her job facilitated or not ?)

Even more complicated than that. The same dataset ID refers to different
products at different times, because the calibration software, or the calibration
reference files change with time. That's the difference between a dataset ID
and a product ID! The dataset ID refers to an observation, while the product ID
refers to one of the many possible instances of that observation.

Alberto M.

--
Alberto.Micol at eso.org                         Tel: +49 89 32006365
HST Science Archive       ST-ECF              Fax: +49 89 32006480
ESA/RSSD/SN               c/o ESO             Karl Schwarzschild Str.2,
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