Re: Base Normal Form

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Fri, 08 Jul 2005 10:47:14 +0200
Message-ID: <42ce3d93$0$93294$e4fe514c_at_news.xs4all.nl>


Nice to hear from you :-)

dawn wrote:
> Jan Hidders wrote:
>

>>dawn wrote:
>>
>>>Jan Hidders wrote:
>>>
>>>>It's really not a good idea to confuse the concept of
>>>>relation and function.
>>>
>>>I definitely agree!
>>
>>And yet that seems to be the consequence of what you are proposing. I
>>could be wrong but I interpreted your suggestion as that every relation
>>with a candidate key is a function.

>
> Yes, that is what I am saying, but I'll try to say it better.
>
> Every database relation can be modeled as a mathematical relation.
> Every database relation that has a candidate key can be modeled as a
> mathematical function as well.

There is a function for every candidate key. That is the somewhat confusing difference here, no?

[snip]

> Every database relation, if defined to require a candidate key, can
> then be modeled as a function. Yes.

So "a function" here should be /functions/.

  [snip]

> It isn't hard to comprehend the differences between a mathematical
> relation and a relation as defined by the relational database
> community, although I'll admit it can be confusing. If I explain data
> modeling to somone not predisposed to talk about "relations" then I can
> just talk about sets and functions and they get it. A function takes
> in a URL and gives you a web page. It takes in a state abbreviation
> and gives you a state name. It takes in an SSN and gives you a name.
> It can be thought of as a set/object as well as a function/actor.
>
> Then we can add in operators (which are, of course, functions) and
> types (sets) and move on to logic (two-valued, please!).
>
> [Then temporal matters and metadata discussions and so on. After that
> we can discuss where the real complexity comes in -- with data stored
> in a human language, determined, entered, searched for, and interpreted
> by humans.]
Received on Fri Jul 08 2005 - 10:47:14 CEST

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