Re: Extending my question. Was: The relational model and relational algebra - why did SQL become the industry standard?

All of your multiset examples involve external physical representations. Why, then, are you suggesting a use for multisets as a logical representation?

"Steve Kass" <skass_at_drew.edu> wrote in message news:b2ulsp$10v$1_at_slb2.atl.mindspring.net...
> Here are a few, including examples where <item, multiplicity> is a
> natural conceptual model and where <item, item, item> is.
> (also see my post previous to this, answering Bernard)
>
> An inventory.
> When I inquire at a bookstore as to the availability
> of a book, someone looks it up in a database and may report "we have
> three in stock". If I purchase one, the physical implementation changes
> a "3" to a "2". It doesn't delete a fact from a table. Similarly, my
local
> pharmacy probably maintains an inventory of medications on hand. I
> doubt that 1,237 tablets of alprazolam are represented by that many
> entries in a database.
>
> Ticket sales.
> "We sold 325 adult tickets and 104 child tickets today."
> The tickets are separate physical entities, and when a family purchase
> several, a machine issues several identical objects (they may well be
> numbered, unfortunately), so this example is one where there is some
> representation of the multiset as individual but identical items.
>
> A receipt.
> SQL Burger $3.29
> Big Int $1.24
> Table Service $.99
> SQL Burger $3.29
> SQL Burger $3.29
>
> Groceries.
> "Could I have two dozen jumbo shrimp, please?"
> "and a dozen eggs?"
> "and 5 pork and scallion buns?"
>
> Perhaps I gave you the impression that I had something more
> subtle in mind, but these are the kinds of things for which I think
> multisets, sometimes conceived as sets of <item,multiplicity> pairs
> and sometimes as true bags, are useful.
>
> SK
>
> >>
> >>
> >
> >Steve,
> >
> >Could you provide a practical example that might help me in wrapping my
mind
> >around the notion of utility for logical models of items with
> >multiplicities?
> >
> >I'm afraid I'm having problems understanding how one can even have some
> >sense of determinancy of what constitutes a multiset in contrast to a set
> >without some implicit logical mapping to identity. In the mind's eye,
the
> >very basis for contrasting a multiset from a set, or vice versa, is
> >dependent on our very notion of identity.
> >
> >For example, if I see {1,1,1,1,1}, I would have a tendency to describe it
as
> >a collection of integer 1 values with a cardinality of five. In the
process
> >of synthesizing my description, I find that I implicitly assign
cardinality
> >to each member even though set theory would reduce this to {1}. Thus, I
can
> >distinguish between the two collections.
> >
> >What am I missing?
> >
> >I guess the root of my confusion lies in the fact that I don't see how we
> >relate to anything in the real world without trying to apply some notion
of
> >identity in a logical sense.
> >
> >>>
> >>>
> >
> >
> >
> >
>
Received on Wed Feb 19 2003 - 04:46:34 CET