Re: What databases have taught me

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Fri, 30 Jun 2006 21:23:46 GMT
Message-ID: <CDgpg.4287$pu3.100814@ursa-nb00s0.nbnet.nb.ca>

Marshall wrote:
> Bob Badour wrote:
>

>>Marshall wrote:
>>
>>>Mmmm, what I was trying to point out is that it is a somewhat
>>>OOish idea to consider functions on a type as part of the
>>>definition of that type.
>>>
>>>Given a set A, and a set B.
>>>Given a function  f: A -> B
>>>
>>>We would not *necessarily* consider f as part of the definition of A.
>>
>>I would. I wouldn't necessarily require all operations defined on a type
>>be declared to the dbms, but the type is a set of values and a set of
>>operations on those values.

>
> Are you saying you "would consider f as part of the definition of A"
> or are you saying you "would necessarily consider f as part of the
> definition of A."

That depends on whether A is a data type or a set. A data type is a set of values and the set of operations defined on those values. (Note that is data type as opposed to the myriad other uses of 'type'.)

> Other question:
>
> given:
> f: A, B -> C
>
> is f part of the defintion or A, or of B, or both? What about C?
>
> Just curious.

f is defined on all three A, B and C. Thus f is part of the definitions of three data types.

> Marshall
>
> PS. While you are at it, I need 500 words or more on
> "what I did during my summer vacation" by next Tuesday.

Hey! I know it sometimes seems otherwise, but this is comp.databases.theory and not comp.databases.do.my.homework.for.me! Received on Fri Jun 30 2006 - 16:23:46 CDT