Explainations of interface/serializations (what is required) (Was: Re: [QUANTITY] Data Model for Quantity v0.5

[Brian Thomas]

	David,

	The missing mappings are from a lack of clarity on my part.. and are 
	implied (by me) as under the "Values" component of the CoreQ. 
	This means that you can either have a set of mapped or explicit "Values".
	To clarify explicitly then, the StandardQ/CoreQ component breakdown
	looks like:

-----
	Core Quantity
                UCD
                CoordSystem
                Units
                DataType
                Values (either explicitly held or from Mapping)
                AltValues
                Accuracy

        Std Quantity
                UCD
                CoordSystem
                Units
                DataType
                AxesList
                Values (either explicitly held or from Mapping)
                AltValues
                Accuracy
-----

	Because Q interface "realizes" Frame, then there is no aggregate component within
	the Q that is called a "frame". If you want a frame from a Q, you can either
	access those parts of the Q that have frame inforation (e.g. axes, coordSystem).
	Optionally, you can just downcast the Q to create a frame, e.g.

	BasicQuantity someQuantity = (BasicQuantity) new BasicQuantityImpl();
	Frame myFrame = (Frame) someQuantity;

	=b.t.


On Monday 10 May 2004 12:54 pm, David Berry wrote:
> Brian,
>       One of the problems which people may have is that the items in your
> list below do not include "Mappings" or "Frames". This illustrates one of
> my concerns that the serialisations in the doc do not seem to describe the
> same model as the interface. It seems like we have two models in the doc,
> one defined by the interface and one implied by the example
> serialisations. Why can we not have a serialisation in which (for
> instance) a CoreQ contains a (Mapping or ValuesList) and a Frame:
>
>    <CoreQ>
>       <Mapping> (or <ValuesList>)
>        ...
>       </Mapping>
>       <Frame>
>       ...
>       </Frame>
>    </CoreQ>


>
> > > Moreover it would be nice to have a clear statement
> > > of which parts are mandatory and which ones are optionnal, at each
> > > level, in clear english (understable by non-english mother spoker like
> > > me)
> >
> > 	This *is* in the document, but may not be clear. OK, I will take a stab
> > at a summary:
> >
> >          Basic Quantity [id attribute optional]
> >                  UCD  -   Optional
> >                  CoordSystem - Optional
> >                  Units - Optional (Defaults to "unitless")
> >                  DataType - Optional (Defaults to "string of arbitrary
> > length") Value - Required
> >                  Accuracy - Optional
> >
> >          Core Quantity [id, size attributes optional]
> >                  UCD - Optional
> >                  CoordSystem - Optional
> >                  Units - Required (But if absent in serialization it
> > defaults to "unitless") DataType - Required (But if absent in
> > serialization it defaults to "string of arbitrary length") Values -
> > Required
> >                  Accuracy - Optional
> >
> >          Std Quantity [id, size attributes optional]
> >                  UCD - Optional
> >                  CoordSystem - Optional
> >                  Units - Required (But if absent in serialization it
> > defaults to "unitless") DataType - Required (But if absent in
> > serialization it defaults to "string of arbitrary length") AxesList
> > (gives coordinate frames for accessing values in Q) - Optional Values -
> > Required
> >                  AltValues - Optional
> >                  Accuracy - Optional
>
> 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                                Tel. 01772 893733
>                                              01257 273192

-- 

  * Dr. Brian Thomas 

  * Dept of Astronomy/University of Maryland-College Park 
  * Code 630.1/Goddard Space Flight Center-NASA

  *   fax: (301) 286-1775
  * phone: (301) 286-6128 [GSFC]
           (301) 405-2312 [UMD]