Re: A Normalization Question

> > ID Person Color Street
> > 1 brown brown brown
> >
> > One only needs to look at the above tuple to see 'brown' is redundant.
> > One can become blind to this obvious fact by seeing things through a
> > limited data model.
>
> I'm not seeing things through any data model in particular.

Whatever data model(s) you are viewing string 'brown' through is/are not allowing you to see that the string 'brown' as a distinct thing from the three other things it names. This is more apparent in TM as shown at www.xdb2.com/Example/ThingsNamedBrown.asp where one string 'brown' names multiple things.

> > Then your/RM's standard definition/theory is limited as changing one
> > 'brown' to 'nworb' in a db with multiple occurances of that string
> > results in unsynchronized data.
>
> That can always happen if you allow changing the database constraints,
> even in your data model. If that is your definition of update anomaly then
> you trivialize the notion because all data models will always suffer
> from update anomalies and that makes this definition worthless.

TM doesn't suffer from the above update anomaly. This can be demonstrated with XDb1 and XDb2.
www.xdb2.com/Example/ThingsNamedBrown.asp makes it apparent that it won't suffer this update anomaly by seeing that even though multiple things are named by 'brown', they all refer to the one and only 'brown' in the whole db.

> > The number of updates have nothing to do with the fact that string
> > 'brown' is redundant in the following tuple:
> >
> > ID Person Color Street
> > 1 brown brown brown
>
> No, but it shows that you are in fact introducing new update
> anomalies that weren't there before.

Irrelvant to string 'brown' being redundant.

> >> whereas your example is a bit exotic, to say the least.
> >
> > It is not for a data model to make a judgement whether something is
> > exotic or not.
>
> You are simplifying certain updates that will probably never occur and in
> doing so you make certain other updates that occur very frequently harder.

It is not for a data model to judge which updates will probably never occur, if it does, it is a limited model. Whether an update is harder (requires more memory or cpu cycles) is irrelevant to the string 'brown' being redundant.

> That's not good data modelling.

Representing the same thing (string 'brown') three times in one db is not good modelling as it can lead to update anomaly. Received on Sun Jul 18 2004 - 05:10:41 CEST