Characterization draft

[Francois Bonnarel]

Dear Anita,

         I am very late in answering your characterization draft mail,
and Mireille's and Jonathan remarks
there is only a few minor issues which i want to comment


< COVERAGE A description should provide at least one Coverage axis ("Axis Frame", "Axis"). 
Isn't that a MUST? Otherwise we allow to have characterization with only Resolution and/or
sampling . Is that what we want ?

<FillFactor 'should' be given on any axis where the actual coverage is significantly less than 1 (i.e. <100%) but the filling is too complex in too many irregular regions to be described practically <using Support or Sampling. FillFactor applies to the usable fraction of data within the whole <Bounds. 
<FillFactor 'may' be given in addition to Support and/or SamplingPrecison in which case: 
<If SamplingPrecison is not given but Support is given FillFactor =/< Support/Bounds 
<If Support is not given but SamplingPeriod and SampleExtent are given FillFactor = <SampleExtent/SamplingPeriod If Support, SamplingPeriod and SampleExtent are given FillFactor <= Support/Bounds * SampleExtent/SamplingPeriod 
<and the data provider should take care that the values and units given are consistent with these <relationships.
    Thank you Anita to have clarified this point. But Currently what we have in the model (schema and UML)  is the following: Fillfactor is in sampling as a substitute of SampleExtent/Sampling
Period which is only part of the relationship. Do we only recommand a method to
give this filling factor or do we move the filling factor to support as a possible substitute to
its current value  (we may have Bounds and then just fillingfactor as a % in the support
element ?) 
   But in that case what do we do with the sampling ratio information?
 
<If there are many areas of Support within the coverage, the Resolution and Sampling Precision <refer to the inside of each Support area and they are assumed to be consistent within each Support <area (if not, each area must be described separately).
Yes, but presently there is no link from the Coverage support to the Resolution support
Resolution support is just a set of intervals defined for the resolution values...
Do you propose to change that? 




<You 'should' give the ErrorRefVal (typical value i.e. Location) You 'may' give the ErrorBounds <for uncertainties which vary along the domain of the axis 
<You 'may' give an ErrorMap (as a URI) to describe the variation of errors with location.
I think in the case Accuracy is allready there (because it has a SHOULD) then we
MUST have either   ErrorRefVal or ErrorBounds

<There 'may' be a flag to indicate Sampling Status (this 'should' be provided where it is customarily <relevant).
Actually there is TWO flags for that  undersamplingStatus and regularsamplingStatus
both should have a MAY


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Francois   Bonnarel               Observatoire Astronomique de Strasbourg
CDS (Centre de donnees          11, rue de l'Universite
astronomiques de Strasbourg)    F--67000 Strasbourg (France)

Tel: +33-(0)3 90 24 24 11       WWW: http://cdsweb.u-strasbg.fr/people/fb.html
Fax: +33-(0)3 90 24 24 25       E-mail: bonnarel at astro.u-strasbg.fr
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