Re: A Normalization Question

> > A data model that decides which type of redundancy is good or not is a
> > limited model.
>
> but using redundant references to a single location storing
> "brown" is not redundant becuase the redundant references
> are metadata, which is okay. Therfore, your own model
> decides which types of redundancy are good and which are not.

In general, references don't need to be normalized. A reference encodes the thing referencing (start point) and the thing referred (end point). In the diagram below, none of the references to red are redundant, because no reference has the same start and end points. While the end point (red) is the same in all cases, the starting point is not. The starting point is implicit while the end point is explict. Because the starting point is implict, the 3's to red appear redundant but aren't because the references are actually 1->3 and 2->3. In the third method of indicating references, I use arrows.

-------RM------ ---XDb1------ ---Brain?--- T_Persons T_Persons T_Persons ID Person Color Person Color Person Color

1  john   3       john   ->3      john   ---| 
2  mary   3       mary   ->3      mary   ---|
                                  __________|
                                  |
T_Color           T_Color         |   T_Color
ID Name           ID Name         |   Name
3  red            3  red          |-> red

www.xdb2.com/Example/ThingsNamedBrown.asp shows how related things can be displayed without showing IDs/Refs unless specificially requested by user as in the third image. Received on Wed Jul 21 2004 - 03:15:11 CEST