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ivoa-std / MANGO

Model for Annotating Generic Objects in VOTables
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ValueRange proposal #33

Closed lmichel closed 1 month ago

lmichel commented 2 years ago

Right now and taking into account the open issues, we can split measures into distinct categories:

Looking at the XMM data, it turns out that many measures in any categories, are valid for a specific range of a given quantity. The perfect example for this pattern is given by the energy bands. Most of the XMM catalogue columns (and Chandra as well) are related to one energy band.

My proposal is to allow any Mango measure to point onto e.g. a ValidityRange object.

lmichel commented 2 years ago

On Mark Behalf

I think we need to base this on a usage thread where the information comes into play. In reading this, I originally thought you meant one thing, but as I got into it, I am not so sure what you mean exactly.

those linked with a coordinate frame meas:Measures are related to a coordinate space, and you can specify the domain range (validity) in the Axis spec. I've done this for CCD positions and PHA energies in the example files.

  • those linked with a photometric calibration Similarly, a photometric measure can assign the axis domain range from the Photometric calibration metadata.

Looking at the XMM data, it turns out that many measures, in any categories, are valid for a specific range of a given quantity.

The perfect example for this pattern is given by the energy bands. Most of the XMM catalogue columns (and Chandra as well) are related to one energy band.

  • These energy bands must be described by the model
  • They must be attached to the relevant measures

But then this part seems to be talking about something else. To me this sounds like: The Flux Measure references the Photometric Calibration which describes the energy band filter applied.

The flux value is 'valid' only for certain ranges of other domains (energy band, time, etc) Which sounds like Characterisation to me.

For Chandra data, you can filter the event list on any time range and energy band, and derive a flux.. this filter info isn't stored in any modeled object. Is this Provenance, or Characterisation or other?

So.. I'll circle back to saying that I'd like to see the usage thread that needs this info.

Mark

lmichel commented 2 years ago

The first example I've in mind is the XMM catalog. Te following measurse are given by energy band:

The top 3 can be considered as photometric data, but the fourth not. It should be mapped on a GenericMeas but it must also be connected with an EB description. The problem yet is not to know how these EBs would be modeled (Char components, Coords classes, ...) but to know where to put hooks on them in the MANGO model.