Re: dbdebunk 'Quote of Week' comment

Marshall Spight wrote:
> x wrote:
> >
> > This means that there must be a one to one mapping between the generated key
> > and some key with a meaning for the end user. Therefore that meaningless
> > primary key is a pointer. But one of the goals of the relational model is to
> > eliminate pointers from the data model.
>
> I'm not sure I share this point of view. I propose that
> every pointer is meaningless; every key is meaningful,
> whether system generated or not. The meaning is exactly
> that it is the identity of the row. A randomly-generated
> customer id still means something.
>
> Another difference between keys and pointers is that
> keys are content-addressible, while pointers are
> location-addressible.

and there have been several prior discussions on pointers that I think got most of us to the point of understanding that the pointers that the relational model were eliminating were related to memory locations. When talking about data that serve as references to other data at the logical level, there is nothing in the relational model that prohibits or even discourages such.

> The differences between keys and pointers are small and
> sometimes subtle, but useful nonetheless.
>
It is interesting to me that the relational model that some say is intended as a logical model for data had as one of its goals a physical issue. What do you make of that? --dawn Received on Fri Aug 26 2005 - 20:10:06 CEST