Re: Demo: Modelling Cost of Travel Paths Between Towns

> > Storing [at logical level] any thing (ie PA) twice is redundant.
>
> A computer represents PA as a string of bits - either 16 or 32 bits on
> most modern computers....

To repeat from OT "A Normalization Question", which you were a significant contributor, how the logical layer of a data model is implemented at the hardware level is irrelevant. The purpose of a logical model is to provide isolation/separation from hardware. At the user level, one should only be concerned with redundancy in the logical layer. You may want to scan old threads by Bob Badour expounding the distinction between the two layers.

> > On way to prove redundancy is to change the second PA and see if data
> > is corrupted (without triggers/code to synchronize them).
>
> ...changing the second PA would in fact even be required.

Thus proving the second PA is redundant.

> > Also, if a property is
> > added to PA, will you add it the first PA, second PA, or both?
>
> You are -once again- showing your total lack of comprehension of
> normalization. If a propert is added to PA, it should be added in a
> seperate table.

Yes, a separate table for states is the correct way to avoid redundant PA's (even if PA doesn't have any properties). Alan didn't provide such a schema thus he has redundant PA's. Also note, the notion of having to add a table in order to accomodate properties is a characteristic of RM and not necessarily that of other data models such TM/XDb2. Received on Sun Nov 14 2004 - 06:37:38 CET