[TRANSFORM] What is a "frame"?

[Ed Shaya]

Here is what we are talking about in a rough, possible serialized form.
I am just guessing that this algorithm would like input in the form of
tuples of the index values (which normally would be generated by some other
algorithm, but here I just type them in).   Frame is now a collection
of the various quantities (epoch, centerRA, centerDE, pixelsPerArcsec, etc)
needed for the transformation.  Sorry, no UML for you Pierre, maybe later.

FluxQ
    Argument
       positionQ
    ValueList
       list of flux values

positionQ
    Argument
          Index(NAxis1)
    Argument
          Index(NAxis2)
    DataFormat
          tuple
               int
               int
    ValueList
          0,0 0,1 0,2 ...
          1,0 1,1 1,2 ...
             ...
    Mapping
         Algorithm
             algorithmID
                 http://ivoa.net/algorithms/WCS/position/iiRaDec.c
         Input
             frame1
     Mapping
         Algorithm
              algorithmID
                 http://ivoa.net/algorithms/WCS/position/iiGalactic.c
         Input
              alternateFrame2


Ed



David Berry wrote:

>Ed,
>
>  
>
>>I am not completely familiar with what is in this Frame object, but I
>>have been assuming it is information on the reference frame.  In which
>>case I agree.  That is not a Quantity. The reference frame information
>>is metadata.  WCS, however, does provide the keywords necessary to
>>describe the axis.  Those keywords are the axis Quantities, in
>>algorithmic or abstract form.  The reference frame info is metadata
>>within that Quantity.
>>    
>>
>
>I think we agree (except for differences in nomenclature) - WCS would
>contain one or more Frames, each Frame describing a coordinate system in
>which the position of a data value within the associated data structure
>can be expressed. The WCS would also contain the Mappings (equivalent to
>"algorithms"?) to enable a position in one Frame to be transformed into
>any of the other Frames.
>
>David
>
>----------------------------------------------------------------------
>Dr David S. Berry    (dsb at ast.man.ac.uk)
>
>STARLINK project                        Centre for Astrophysics
>(http://www.starlink.ac.uk/)            University of Central Lancashire
>Rutherford Appleton Laboratory          PRESTON
>DIDCOT                                  United Kingdom
>United Kingdom                          PR1 2HE
>OX11 0QX
>
>
>  
>