Re: database design method

Leandro Guimarães Faria Corsetti Dutra wrote:
>Jan.Hidders wrote:
>> In article , Leandro Guimarães Faria Corsetti Dutra wrote:
>>
>>> Wrong, ER can't capture all of the organisation's rules, because it
>>> has no equivalent to all integrity constraints in the database.
>>
>> Sure it has. It can use the same language that you can use for the
>> relational model: 1st order logic.
>
> Now I want to see it. References, please. You may want to be
>informed of articles against your view in http://dbdebunk.com./, for
>instance.

Dbdebunk is not the gospel. The fact that you can use FOL to describe constraints in the ER model is so plainly obvious to people who know about logic and ER models that no serious researcher would write an article about that.

If you think there is an inherent problem there then I suggest you share it with us and I will be happy to explain why it isn't a problem. :-)

> BTW, it is not simply "1st order logic", but Set Theory *and* 1st
> Order _Predicate_ Logic.

Yes, predicate logic, any other first order logics you know? :-)

But what makes you think you need set theory to specify constraints? Is there any constraint expressible in set theory but not in logic? What you _may_ sometimes need is higher order logics to express constraints you cannot express in FOL, but that's about it.

• Jan Hidders