Information Systems Base Language (ISBL) and followed the relational model very strictly. Even features such as user-defined functions were formalized within that model. The PRTV team also introduced surrogates to the relational model to help formalize relational update operations; and a formalisation for updating through views. However neither of these was implemented within PRTV. PRTV emphatically did not implement NULL values, because this conception was introduced only in 1979.

PRTV was itself never available as a product, but