  The theory of triples of Poisson brackets and related integrable systems,
based on a classical R-matrix R in End_F(g), where g is a finite dimensional
associative algebra over a field F viewed as a Lie algebra, was developed by
Oevel-Ragnisco and Li-Parmentier [OR89,LP89].
  In the present paper we develop an "affine" analogue of this theory by
introducing the notion of a continuous Poisson vertex algebra and constructing
triples of Poisson lambda-brackets. We introduce the corresponding Adler type
identities and apply them to integrability of hierarchies of Hamiltonian PDEs.
