ranges

[Elizabeth Auden]

Hi all,

> capabilities, all use range specifications for quantities such as bandpass
> coverage.  The RSM V.6 document generally does not do this.  In fact, I have
> a bit reluctant to put in specific metadata elements for upper and lower
> limits, as they are often poorly defined (what are the exact wavelength
> limits for various optical filters?), I am not sure they will be terribly
> helpful in locating data of interest, and they increase the burden on the
> data provider in registering their resources.

I think extreme fuzziness would be a good approach.

I've just talked to some of the MSSL x-ray astronomers, and one of them
brought up an interesting complication.  In a recent XMM-Newton proposal,
they had to define ranges in terms of both electronVolts and angstroms for
the same object being observed on the same satellite - just in two
different intstruments.  So, whatever "wavelength" conveys in the registry
standards, we should make sure that it can cover length, frequency, and
energy.  Even using words like "soft x-ray" as a range could be misleading
since the range of soft x-rays can be 0.1 - 2 keV (soft for extragalactic
observations) or 2 - 10 keV (soft for x-ray binaries).

> non-trivial to say exactly what the lower and upper wavelength limits would
> be.  Moreover, if I were to select particular limits, say at lambda max of
> 9000 angstroms, and someone submits a query to the registry looking for data
> at 9005 angstroms, would we want to steer them away from HST?  I don't think
> so.

The best I can come up with after only one cup of coffee is to suggest
that we have wavelength ranges that are as broad as possible (for example,
"soft x-ray = 0.1 - 10 keV), and allow a toggle for users to say "+/- 0.5
keV" or similar.  That way, a query for 8000 - 9000 angstroms +/- 100
angstroms would still include HST at 9005 angstroms.

My thought on this is that it's better for the registry to return too much
data rather than too little; the user can always narrow down the query.

cheers,
Elizabeth