Re: database design method

Jan Hidders wrote:

> Leandro Guimarães Faria Corsetti Dutra wrote:
>

>> Jan Hidders wrote:
>> 
>>> Where exactly in those articles do they claim that you cannot use
>>> FOL to describe constraints in the ER model?
>> 
>> No, they claim that ERDs can't represent all possible constraints.

        The RM can represent all machine-enforceable constraints AFAIU. If I'm in the wrong, please prove so.

> But I said that you can use FOL to describe constraints in the ER
> model. So if you extend the ER model with FOL (which is not very
> difficult) then you can describe those constraints.

        What do you mean by "extend the ER model with FOL"?

        If it means complementing ERDs with textual representations of constraints, then we just have proved ERDs aren't enough. Then it is just a matter of taste or circumstancial expediency to draw diagrams for quick visualisation and later flesh them out with test, or to go straight for text and later draw parts for presentation. As we wanted to prove.

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