Re: Logical equivalence of simple and complex types under the relational model?

"Paul" <paul_at_test.com> schrieb im Newsbeitrag news:41acdfd0$0$9345$ed2619ec_at_ptn-nntp-reader02.plus.net...
> Rene de Visser wrote:
>>> If the DBMS has a function that returns the integer part of a float,
>>> this means that float is a complex type?
>>
>> I was wondering about such things myself. What if you have a function
>> that returns that the nth bit of an integer? Or allows you to do
>> prime decompositions of a number?
>>
>> I am not sure that the split between complex and simple is well
>> defined at all. Especially if the DBMS allows user defined functions
>> that can operate on the phyiscal level...
>
> The way I see it, DBMSs consist of two (orthogonal) components: a type
> system and a relational system. If the DBMS can decompose a value using
> the relational system alone, it's a complex value. If it needs the help of
> the type system to decompose the value, it's a simple value.

In AP5 the type system and relational system are very well integrated. Types are relations of arity 1.
Relations can be defined by algebraicly using WFF's (well formed formulas) on a model algebra over relations.
Relations can be defined by function.
And functions can be defined using WFF's (in addition functions can be defined using common lisp functions, so that its not totaly circular)

As such your classification above doesn't help in classifying values as simple or complex in AP5.

>
> Like most things, "complex" and "simple" are relative terms. To the type
> system pretty much all values are complex. To the standard relational
> system, all values are simple.
>
> Paul.
Received on Tue Nov 30 2004 - 23:21:27 CET