Re: What databases have taught me

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sat, 01 Jul 2006 02:02:41 GMT
Message-ID: <5Jkpg.4388$pu3.102482@ursa-nb00s0.nbnet.nb.ca>

Marshall wrote:

> Keith H Duggar wrote:
>

>>all functions operating on a given data type are part of the
>>/definition/ of that data type, doesn't seem useful, at
>>least in a programming context. Why are we not free to
>>choose which operations /define/ a data type and which are
>>merely /auxiliary/ or /derived/. How is it useful to think
>>that anytime we define functions we are redefining the types
>>of it's arguments?

> 
> I too have this question. What is the utility? What is gained,
> or what would be lost if we didn't do this?

If the data type is a set of values and the set of all operations defined on those values, then the operation is part of the data type regardless whether it appears in a program's text. One does not have to enumerate all of the values of the type. Why would one have to enumerate all of the operations? Why would the subset of enumerated operations alter the data type?

Almost all relation types will never have all of their values instantiated. In fact, most will only have a tiny fraction of their values ever instantiated. Why should it be any different for the operations of data types? Received on Fri Jun 30 2006 - 21:02:41 CDT