Re: database design method

Bob Badour wrote:
>"Jan Hidders" <hidders_at_REMOVE.THIS.uia.ua.ac.be> wrote in message
>news:3dd011dd$1_at_news.uia.ac.be...
>> D Guntermann wrote:
>> >
>> >Moreover, Mr. Date, in chapter 11, does go on to say that it seems
>> >prefereable to avoid relation-valued attributes, at least for base
>> >relation variables in most cases, because they are asymmetric and
>> >provide a degree of needless complexity.
>>
>> I fully agree with Date here. In fact, I would even go further then that.
>> IMO we should stick with the original flat interpretation of the
>> relational model, (so not even relation-valued attributes) but with the
>> addition that we allow domains of abstract identifiers (or object
>> identifiers if you want to call them that).
>
>With user defined types, one can define whatever type one wants.

That depends upon what the minimal requirements are for defining it. If I have to define a function that outputs the representation of the value then there is a problem. It also depends on how exactly you can denote or create new values. As long as these things are not exactly specified it is not clear if you can use abstract identifiers or not.

• Jan Hidders