Re: More on lists and sets

Jan Hidders wrote:
> David Cressey wrote:
> >
> > [...] A cursor is a named query, declared in the
> > context of a user process (program), that can be invoked to play the role
> > of a list. I haven't seen cursors discussed as if they were lists, but it
> > seems to make an eminent amount of sense to me.
>
> Really? Cursors are an inherent procedural concept and I would think
> that is the last thing you want in what should be a declarative query
> and manipulation langauge. Moreover, integrating lists and bags into a
> declarative set-oriented language is basically a solved problem as the
> required ideas, knowledge and experience is already available in the
> literature, although it is sometimes dressed up as "nested relational",
> "object-oriented" or "xml" research.

I would suggest that nesting phenomena is independent of set-bag-list hierarchy. See the theory of bunches by Eric Hehner: "From Boolean algebra to Unified Algebra" -- a chatty paper that only mentions bunches at page 12.
"Unified Algebra" -- more formal one. Received on Mon Mar 27 2006 - 20:48:59 CEST