Approach to metadata for Spectral Data at the Planetary Data System (PDS)

[Markus Demleitner]

Hi Anne,

Thanks again for your insights -- it's interesting to see how many of
the problems we're struggling with are being addressed in a
different, if closely related community.  I'd be very grateful if you
could keep an eye on what we do with our product-type vocabulary.
While from what I see it seems to me that its use case is
so different from what you do in PDS that we probably can't just
"import" something from your metadata scheme, we should at least make
sure that things don't seriously conflict.

And while this bit is quite a bit outside of semantics proper, let me
offer another remark:

On Tue, Jun 15, 2021 at 11:52:38AM -0400, Anne Catherine Raugh wrote:
> There is no Array_1D_Spectrum because 1D spectra are not presented as
> arrays. That looks like the single biggest problem we'll have making our
> linear (that's how I think of them) spectra available through an IVOA
> interface. Linear spectra are present in the archive in one of two formats:
> Either a table, where each row describes the measure value and all related
> parameters for one spectral bin; or as a table where each row contains one
> spectrum and related data for each bin. The vast majority of the time,
> these tables are ASCII, not binary. And the column content varies so widely
> that attempts to define standard column sets have failed. No attempt was
> ever made to define standard column names, because there was no enforcement
> mechanism apart from fallible (and fickle!) human review.
> 
> I suspect there are some binary spectral tables in the archive I've
> forgotten about, and when we get to the realm of radio data I would expect
> binary rather than ASCII data. I always have to find an expert when I need
> to understand what is going on in a radio data set.

Don't sweat the actual data sets *too* much.  While clearly it'd be
great if we had more takeup of the spectral serialisations the IVOA
recommends at this point (https://ivoa.net/documents/SpectrumDM/,
parts 3 and 4), many of our spectral services push out the weirdest
sorts of files, too.  So I'd always say: *findable* is already
valuable, even if the *usable* part might come with strings (as in
"quite a bit of manual work") attached.

Thanks,

         Markus