Re: Modeling Address using Relational Theory

dawn wrote:
> Marshall Spight wrote:
>

>>Gene Wirchenko wrote:
>>
>>>On 29 Aug 2005 20:49:44 -0700, "dawn" <dawnwolthuis_at_gmail.com> wrote:
>>>
>>>>I understand the Line1, Line2, Line3 implementation, but any model with
>>>>those attributes screams "this model is not relational", right?  I am
>>>
>>>     No.  It is not 1NF if the attributes can have other than one
>>>value, but the names are irrelevant except that they be unique within
>>>the relation.
>>
>>Agreed. Line1 and Line2 are not two interchangable instances of
>>the same kind of thing; they are specific distinct fields. It
>>is not a repeating group.

but this group certainly is!

  but I thought that having
> Major1, Major2, Major3 or AddressLine1, AddressLine2, AddressLine3
> violated relational modeling principles. Are you saying that this is
> just fine? If I understand correctly, it is fine because line1 is the
> first line, where line2 is the second line, so they are different
> attributes?

i believe it's "fine" in the sense of not forbidden and the reason is definitely not that one comes "first" and another "second". those meanings are quite external.

So, if you want to have a person's name and up to 4 of
> their former names, does it violate relational principles to have these
> as attributres Name, FormerName1, FormerName2, FormerName3,
> FormerName4? ...

i'd say the answer is no, it doesn't violate relational principles. application functionality and esthetics are outside the bounds of the RM. i don't know exactly where i've read this, but it makes sense to me, unless and until the RM can show that it can solve all possible external design problems. but it is still wrestling with some aspects of its own design, so i would say the former hasn't happened yet.

cheers,
p Received on Tue Aug 30 2005 - 21:35:32 CEST