  The relational version of the modal interpretation offers both a consistent
quantum ontology and solution for quantum paradoxes within the framework of
nonrelativistic quantum mechanics. In the present paper this approach is
generalized for the case of relativistic quantum field theories. Physical
systems are defined as Hilbert spaces. The concept of the reduced density
matrix is also generalized so that its trace may become smaller than one,
expressing the possibility of annihilation. Superselection rules are shown to
follow if the whole Universe has a definite electric charge, barionic number
and leptonic number.
