Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> comp.databases.theory -> Re: curiousity of sets of no relations?
paul c wrote:
> Bob Badour wrote:
>
>> paul c wrote: >> >>> ... >>> That seems a practical motivation. In terms of relations and/or set >>> theory/predicate calculus can anybody give a more theoretical one? >> >> He simply defined them as the identity elements for the specific >> operations just as one defines any aggregate/fold of zero elements >> using the identity element for the base operation.
Exactly so. And exactly the same way Graham, Knuth and Patashnik define aggregation in _Concrete Mathematics_. We define the iteration over zero items as the identity element of the base operation. Sum() = 0, Product() = 1, Min() = max_value_of_type, Max() = min_value_of_type, etc.
Mathematicians define aggregations that way on utilitarian grounds. Received on Sat Jun 10 2006 - 13:35:15 CDT