> No it isn't, its just mis-stated. What he actually wants is projections,
> which are perfectly sound. That is, given a concrete record with N
> fields, a collection of *views* which only expose a subset of the
> fields.
> 
> More generally, not just a subset of fields, but a new record
> which is the image of a epimorphism (a structure preserving
> surjection or 'onto' mapping).
 
Hi,

I wasn't familiar with the "projections" terminology, but that is
precisely what I meant, and what I've referred to as "marble carving"!
(The wheel keeps getting reinvented...)

Incidentally, are projections implemented by any language out there?
(I realise that to a certain extent, SQL views are also projections.
But what about other examples?)

Cheers,
Dario





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