Re: Navigation vs Relational operators

D Guntermann wrote:
>
> Relational is still navigational, but logically. The relational model frees
> us from physical navigation and somewhat from logical navigation. To
> further provide users the capacity to have even greater freedom from logical
> navigation (e.g. specifying an attribute independent of knowledge and
> application of table names, relationships, and joins), Ullman and others
> (Fagin,Maier and Valdi) proposed and explored the concept of the Universal
> Relation. There was quite an interesting and uncharacteristically blunt
> public debate between proponents of the universal relaton assumption and
> William Kent.
>
> Refererences:
> Fagin, R., Mendelzon, A., & Ullman J.. (September, 1982). A simplified
> universal relation assumption and its properties. ACM Transactions on
> Database Systems (TODS) 7: (3).
>
> Kent, W. (December, 1981). Consequences of assuming a universal relation.
> ACM Transactions on Databases (TODS), 6:(4).
>
> Ullman, J. (December, 1983). On Kent's 'Consequences of assuming a
> universal relation'. ACM Transactions on Databases (TODS), 8:(4).

Probably nobody's interested in this anymore, but I just found a nice short and accessible on-line presentation of the issues and positions:

   http://www-db.stanford.edu/jdu-symposium/talks/mendelzon.pdf

Nice stuff, especially if you know a little the persons involved. If only there were heated debates over *this* subject in this newsgroup... :-)

• Jan Hidders