Date: Fri, 02 Nov 2007 13:18:40 GMT
"Roy Hann" <specially_at_processed.almost.meat> wrote in message
> "David Cressey" <cressey73_at_verizon.net> wrote in message
> > "paul c" <toledobythesea_at_ooyah.ac> wrote in message
> > news:DetWi.165783$Da.130771_at_pd7urf1no...
> >> Bob Badour wrote:
> >> > paul c wrote:
> >> ...
> >> >>
> >> >> I'm wondering are there applications where RVA values that are
> >> >> make sense or are such values just a curious by-product of RVA's?
> >> >
> >> > Yes, of course, there are lots of such applications (assuming RVAs
> >> > sense.)
> >> > ...
> >> For example?
> > The set of toppings on a pizza.
> We've been here before. The toppings on a pizza is more like a list (or a
> set of lists) because some people, like me, insist that the fresh tomatoes
> go on last, and I don't much care what order the peppers and the sausage
> on, as long as they go on before the cheese. Silly, but illustrative.
Ahh, good. I've waited since 2003 for someone in this newsgroup to tell whether the toppings on a pizza are a set or a list. Until your answer, just now, no one really rose to the challenge. Thanks!
Your answer raises the question of whether in a pizzeria like Domino's, the order of toppings stated by the client should be preserved in the order, so that the chef can honor the customer's wishes, or whether it should be retained as a set, and let the chef exercise judgement (or conform to standards) with regard to the order that the toppings are added.
This is pretty far afield of database theory. However, participants in the newsgroup expend a great deal of effort discussing whether list processing systems like Lisp are suitable for representing sets, and also whether set processing systems like SQL are suitable for representing lists (or trees, by extension).
It's clear that a set can be stored in a list, by simply allowing order in the list to be an arbitrary and capricious feature added to the representation. It's likewise clear that a list can be stored in a set of tuples, simply be adding an attribute that determines order in the list. Nevertheless, the boundless energy of the participants continues to raise this issue, from time to time. Received on Fri Nov 02 2007 - 14:18:40 CET