Implementation of the normalized data model does not demand that consequence. If you are using a single RDBMS as your back-end store, you can craft code to take advantage of SQL joins. On the other hand, one also needs to consider the load to be supported. The failure to take advantage of the efficiencies the RDBMS might offer may be overshadowed by other efficiency gains found in not depending on the back-end. One could conceivably have different entities stored using different mechanisms. DBI can make that practical.

My main focus is on the data model itself. For many problems, a good data model is critical and will make the implementation choices clearer. Certainly, the design does not stop there; one has to consider whether the persistence mechanism(s) are homogenous or heterogenous.

Class::DBI has appealed to me as a very handy layer to puy between a collection of objects and the data-store. Your mileage may vary.

yours,
Michael