Proposal to split out the "members" from coreQ (Was: Re: Philosophy of basic Q)

[Brian Thomas]

On Tuesday 11 May 2004 03:11 pm, David Berry wrote:
> On Tue, 11 May 2004, Brian Thomas wrote:
> > > Also, no one seems to have noticed that CoreQ allows for either arrays
> > > or components (parent-child structure) BUT NOT BOTH at the same time!!!
> >
> > I have noticed. In our original proposal this was called a "quantityset".
> > In the implementation I am working on, I have a QuantitySet class which
> > only takes members, and a "ListQuantity" class that only takes values.
>
> What is a QuantitySet?

	A quantity which is a composite of other quantities. Effectively, the
	"CoordsQuantity" *is* such a thing as it holds axes (which are Quanitities).
	Currently "CoordsQuantity" meets the interface of "CoreQuantity".

>
> What are "members"?

	The quantities which are inside another quantity and represent "data".

>
> > 	Look,  we agree on the following :
> >
> > 	We *do* need a quantity which is a composite of other quantities.
>
> Why? What do you mean by "composite"? Do you mean that the values stored
> in the Quantity are themselves Quantities, or that a Quantity holding a
> list of 2-D values can be split into a pair of 1-D quantities?

	Yes, the values stored inside the quantity are themselves quantities.

>
> > All that is needed then is to create a QuantitySet/CompositeQuantity
> > interface by peeling off the needed methods from coreQ.
>
> Why? What does this give us?

	As I said above it is needed for use as "CoordsQuantity", although it
	has use as a means to replicate tables and other things which are
	quantities composed of other quantities.

>
> > I don't believe it is too late to revise this to separate out the
> > "member" stuff from Core/Standard Q and put it in a separate interface.
> > What do other people think?
>
> I think that this is all new stuff which I for one have not seen clearly
> defined or justified anywhere. I think you need to start from the
> beginning and say clearly what a QuantitySet is and why it is needed.

	You have seen it, it exists in the current serialization. The language is 
	just perhaps different from what you have heard before.

	-=b.t.

>
> 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]