Re: Requirements for update languages?

Lauri Pietarinen wrote:
>> >
>> > B1 x B2 = { ( x, n+m ) | (x, n) in B1, (x, m) in B2 }
>>
>> Ahem, that should of course be n.m, i.e., n times m, and not n+m. :-(
>
>Yes, it did look a bit strange...
>
>But just to clarify things, n and m are cardinalities, right?
>
>B1 = {(0,2 )} and B2 = {(1,1),(2,1)}
>
>if applied to the original example?
>
>But these are sets? So what do they have to do
>with bags?

They are bags, or, to be more precies, that's how bags are usually defined: functions that map some set to the set of natural numbers, and functions in turn are usually defined as binary relations that are functional and total. And, yes, that confirms Date's point.

• Jan Hidders