Domains of functional dependences in databases

We consider a solution to the problem of designing a database schema allowing for the presence of null values. This urgent problem still has no satisfactory solution. A new formal theory should generalize the classical theory: the removal of null values should reduce the generalized theory to the classical theory. The existing theories do not satisfy this principle: the system of axioms is changed, new operators of relational algebra that cannot be implemented in the SQL are introduced, etc. We propose an original solution to this problem based on the dependence domain.