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

[David Berry]

Pierre,

> > I always thought we were way ahead of ourselves in diving into
> > serialisations before we had firm agreement on the data model which we
> > were supposed to be serialising!
> >
>
> Well, speaking of data structures (data member inside class) certainly,
> but concerning interfaces your point is not so straigthforward,
> ans serialisation is important beacause it is, then, the only way (?sure)
> to exchange "object" (quantity) as a whole, in one "transaction".

I expect that there will be more than one way to serialise a Quantity
object. The obvious example is FITS - a FITS image is a serialisation
of a Quantity, but it has no relation at all to the XML serialisation in
the doc. VOTABLE is another possible example - we presumably want to
see a VOTABLE as a way of serialising one or more Quantities. And there
could be other forms of serialisation. The only point in us including any
suggested serialisation in the doc, is to ensure that we have at least one
serialisation which is loss-less. But it willbe easier for everyone if
this suggested serialisation has a *clear* and *one-to-one* connection to
the interface.

What I hoped is that the community would argue about the actual *data
model* as described in the interface, until we have agreed on the data
model, and *then* we would decide on a preferred loss-less serialisation.

I believe an interface is the correct way to describe a data model, rather
than a serialisation. An interface says "in order for an object to be
considered an instance of this data model, it should be possible to do
this and this and this with it - how it is stored is immaterial". With
this information, we can write code to process Quantities, no matter how
they are serialised.

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
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