Canonical Models for Representations of Hardy Algebras

In this paper we study canonical models for representations of the Hardy algebras that generalize the model theory of Sz.-Nagy and Foias for contraction operators. The Hardy algebras are non selfadjoint operator algebras associated with $W^*$-correspondences. This class includes the classical $H^{\infty}$ algebra, free semigroup algebras, quiver algebras and other classes of algebras studied in the literature.