Re: database design method
Date: Thu, 31 Oct 2002 14:49:14 +0100
Message-ID: <aprccr$4bud9$1_at_ID-148886.news.dfncis.de>
Jan Hidders wrote:
> Leandro Guimarães Faria Corsetti Dutra wrote:
>
>> Jan Hidders wrote:
>>
>>> Leandro Guimarães Faria Corsetti Dutra wrote:
>>>
>>>> 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.
>>
>> No, but it is a nice reference site and eye-opener.
>
> Sure, but that doesn't mean that everything they say is true. So
> pointing to an article of theirs and say "and therefore you are
> wrong" is not a good argument.
I don't think I did. I only pointed to it for interesting, useful arguments in case you weren't aware of them.
I said "you were wrong" yes, and then asked myself to be proven wrong. But I never offered DBDebunk as any kind of proof, even because I beware of the argument from authority.
>>> 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. >> >> What about Fabian Pascal as "serious"? What about >> http://dbdebunk.com./fp4a.htm as an article? Or take Date and >> http://dbdebunk.com/kimball1.htm.
>
> 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. They are not arguing limitations on first-order logic, but on ERDs.
Now, I never saw ERDs proposed as a complete, practical representation of neither logic nor a relational database. I would love to be proved wrong, because this would make the RM itself more palatable to GUI weenies that currently dominate all over the world.
>>> 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. :-) >> >> OK. How do you express non-RI constraints? How one does express >> each domain, attribute, relation and database integrity >> constraints? Or in a different taxiology, take transition >> constraints, how would ERDs
> represent
>> them? I'm not saying you mightn't have a partial answer, but I >> very much doubt you could give (or point to) a complete answer.
>
> All of the above can be done in first-order logic with the obvious
> limitation that you cannot express what you can express in
> higer-order logics but not in first-order logic. Again, what do you
> think is the problem? You do know what first-order logic is, do you?
Again, how can all of first-order logic be represented in ERDs?
-- _ / \ Leandro Guimarães Faria Corsetti Dutra +41 (21) 216 15 93 \ / http://homepage.mac.com./leandrod/ fax +41 (21) 216 19 04 X http://tutoriald.sourceforge.net./ Orange Communications CH / \ Campanha fita ASCII, contra correio HTML +41 (21) 644 23 01Received on Thu Oct 31 2002 - 14:49:14 CET