Why the relational data model can be considered as a formal basis for group operations in object-oriented systems

Relational data model defines a specification of a type "relation". However, its simplicity does not mean that the system implementing this model must operate with structures having the same simplicity. We consider two principles allowing create a system which combines object-oriented paradigm (OOP) and relational data model (RDM) in one framework. The first principle -"complex data in encapsulated domains" -is well known from The Third Manifesto by Date and Darwen. The second principle --"data complexity in names"-is the basis for a system where data are described as complex objects and uniquely represented as a set of relations. Names of these relations and names of their attributes are combinations of names entered in specifications of the complex objects. Below, we consider the main properties of such a system.