Re: Base Normal Form

From: Gene Wirchenko <genew_at_ucantrade.com.NOTHERE>
Date: Tue, 12 Jul 2005 16:45:56 -0700
Message-ID: <val8d1lgc738q3h4bhmu31p4c9cav286jj@4ax.com>

On 12 Jul 2005 13:41:28 -0700, "dawn" <dawnwolthuis_at_gmail.com> wrote:

>Gene Wirchenko wrote:

[snip]

>> If you say that the ordering is significant, then
>> (a,b,c)
>> and
>> (a,c,b)
>> are different. If you go purely by the name, they are the same. (I
>> have omitted the types for simplicity. Assume that they are the
>> same.)
>>
>> This does not look like much, but consider a join. Now, you have
>> to define which order the columns are in the join. Make sure you do
>> it right, or you could end up with A join B and B join A resulting in
>> different orderings.
>
>I don't say that ordering is significant AT ALL, but I do say that
>using the term "relation" and then insisting that tuples be unordered

                                                   ^^^^^^^^^^^^^^^^^^^
     No, not insisting that tuples be unordered, but that their order

is irrelevant to the RM and that you can not count on any specific order.

>is redefining the term, thereby muddying terminology and notation
>unnecessarily, in my opinion.

     Different contexts, different definitions.

     I think there may a question of which tuples are being referred to.

1. There are the tuples that define the relation. These are unordered for the reason I give above.
2. The tuples of data are also unordered. If you request data, you will not get it in any particular order unless you specify the order. (If it does not matter what order the data comes to you, then why have an order, even an implicit one? If it does matter, then specify the order you want.)

     I have no problem with either lack of ordering.

[snip]

>taking. Every time there is a term with multiple definitions,
>particularly if the defs are mutually exclusive, I might initially be
>frustrated, but eventually I settle on "amused," perhaps as a coping
>strategy.

     I get amused from time to time, too, but I watch it closely. Too much amusement may mean that I am missing the point of something.

>But I will admit that I have more questions than answers.

     The knowledge I prize the most is the knowledge of what I know and what I do not know.

Sincerely,

Gene Wirchenko Received on Tue Jul 12 2005 - 18:45:56 CDT