Bob Badour wrote:
> Marshall wrote:
>
>> Let us consider the choice of characters to use for
>> relational operators. It might be desirable to use
>> different characters for the relational operators from
>> the scalar ones, so we avoid using * for join, even
>> though it is in some sense a product operator.
>>
>> Set subtraction already has a standard character
>> in common usage: \
>>
>> But we also need a character for relational division.
>> The / character is often used, but that's the same
>> as numerical division. Bummer.
>>
>> So, if you had to choose an ascii character for
>> relational division, which one would you use
>> and why?
>
>
> Does a unique relational "division" exist? If "product" has a completely
> different name "join", why should a "divide" use the same name?
>
> If we have an equality operation for relations, does a "divide"
> operation give us all that much?
Hmmmm... and division isn't really the inverse of join. It is the
inverse of cross product which is a special case of join. Is the divide
operation you contemplate the inverse of cross product or a more general
operation which is the inverse of join?
Received on Sat Mar 31 2007 - 11:55:03 CDT
