# Re: I think my book may be wrong about cardinality, but I'm not sure

From: Bruce C. Baker <bcb_at_undisclosedlocation.net>
Date: Thu, 26 Jul 2007 11:21:01 -0500
Message-ID: <TQ3qi.7801\$gZ1.1194_at_newsfe21.lga>

"Cimode" <cimode_at_hotmail.com> wrote in message news:1185462964.626601.174460_at_d55g2000hsg.googlegroups.com...

```> On 26 juil, 16:38, "Bruce C. Baker" <b..._at_undisclosedlocation.net>
> wrote:
```

>> "Cimode" <cim..._at_hotmail.com> wrote in message
>>
>>
>> > On 26 juil, 03:13, "Bruce C. Baker" <b..._at_undisclosedlocation.net>
>> > wrote:
>>
>> <snip>
>>
>> >> Each tuple in a relation with N attributes corresponds to a point in
>> >> an
>> >> N-dimensional space, with each attribute being orthogonal to all of
>> >> the
>> >> others.
>> > What does that mean ? How is a single attribute orthogonal to N-1
>> > attributes part of the same relation?. What do you exactly designate
>> > as *orthogonality*? Why would a tuple necessarily be a point and not
>> > a line ofr plane in geometrical N-space?
>> > What about degree 0/1 relations? How does a degree 0 relation
>> > represent a point in space?
>>
>> The answers to all your questions can be found in any linear algebra
>> textbook.
>
> Really? Would you care providing a source?

"If a relation has /n/ columns, then /each row in that relation represents a point in n-dimensional space/--and the relation as a whole represents a set of such points. In other words, a relation of /n/ columns is /n/-dimensional, not two-dimensional. *Let's all vow never to say "flat relations" ever again.*"

"Date on Database", ISBN 1-59059-746-X, page 371

As for a linear algebra textbook, there are thousands of them. Pick one and make the necessary extrapolation to relational database theory. Received on Thu Jul 26 2007 - 18:21:01 CEST

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