[Passband] a useful self-contained model?

[Martin Hill]

I originally put up the Passband model example (at my mini course in OOD at the
IVOA Interop) as an exercise after fiddling about with some ideas on the twiki
(see DataModelPassband) but after talking to people I think it might be an idea
to develop it.

The intention is 1) to provide a passband model that can be 'plugged in' to the
SED model (from SSA) and ObsData when it is ready, and 2) to practice modelling
a relatively self-contained concept that is familiar to everyone, yet likely to
be viewed and stored and used in different ways by different disciplines.

I've read several documents from several people (and will hopefully be receiving
some more over the next few days) and I think this would be a good opportunity
to get this rather useful bit right and written down and agreed for the VO,
without all the other baggage that is sometimes associated with passbands (such
as velocity...)

If you think this is a waste of time and there is a model you are all happy
with, then obviously feel free to say so (I don't know why I said that, I can't
think of any shy people here).

If not, here are some questions:

  - I'm using Jonathon's term 'Fravergy' (or 'Photon' as the same thing on some
twiki pages) for the 'Frequency/Wavelength/Energy' property of a photon.  I like
it, but please let us know if you don't and have some term that sounds a little
less Monty Python...

  - Who needs errors on passrate()?

  - Is 'passrate(Fravergy)', returning a value 0-1 probability, sufficient for
Radio, X-Ray, etc?

  - Is a simple Min/Max sufficient for the limits of the passband?

  - Does anyone tend to use Passbands as just an error on the frequency on a
measured flux? ie, should Passband also be an Accuracy, or be able to provide an
Accuracy, for things like plots?

  - What else?

I expect we will end up with something far too comprehensive in our requirements
to be useful, so the next set of arguments (er, discussions) are likely to be
about what gets modelled for EverydayPassband and what gets moved to
RadioPassband or XRayPassband or ReallyComplicatedScaryPassband...

Similarly we may also find a split in purpose; a Passband used in 'metadata'
*might* be different from one associated with a Flux for an SED.

I mention these so we don't get too caught up in the existing model. However I
would like to use it as a starting point (the second iteration in my approach
slide) but want to concentrate on first writing down a summary of what we all
need to know about passbands (and only passbands...).

Cheers,

Martin


-- 
Martin Hill
www.mchill.net
+44 7901 55 24 66