Jean-Marc Orliaguet wrote:

If you use a primary key to collect all the dyadic relations into a
unique relation, then you have implicitly created a triadic relation
(identified by the key), except that you also explicitly enumerate the
underlying relations. So in the end you'll have to store: the primary
key + 3 dyadic relations between 6 elements.


Yes, I was just saying that is possible to use only binary relations throutgh projections on a pure expressive power viewpoint by using theprimary key trick. In practice, this might seriously impact the perfomance of the data model since it implies a lot of join operations where a single select should be sufficient.

Furthermore, using binary projections instead of n-ary predicates make it much harder to a human to quickly understand the model.

Regards,

--
Olivier

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