Re: more closed-world chatter

"David BL" <davidbl_at_iinet.net.au> wrote in message news:1178377225.112732.324630_at_e65g2000hsc.googlegroups.com...
> On May 5, 3:16 am, Marshall <marshall.spi..._at_gmail.com> wrote:
>
> [snip]
>
> > def pricedomain = set {1, 2};
> > def anotherdomain = set {3};
> >
> > def R1 = set(price) [price : pricedomain] {(1)};
> > def R2 = set(price) [price : anotherdomain] {(3)};
> >
> > def R = R1 & R2;
> > ---
> >
> > At this point, what is the value of R?
> >
> > R = set(price) [price:pricedomain; price:anotherdomain] {};
> >
> > Since the union of pricedomain and anotherdomain is empty:
>
> IMO it's confusing to talk about taking a "union of the constraints".
> In a sense you are aggregating them. I would call it an ANDing of
> constraints as boolean valued expressions, which leads to set
> intersections not unions.
>
Sorry to add to the confusion, but I will: the union of the constraints yields the intersection of the data. Clear as mud? Received on Sat May 05 2007 - 19:04:32 CEST