A rigorous method is proposed to describe and classify the topology of
entanglements between periodic networks if the links are of the Hopf type. The
catenation pattern is unambiguously identified by a net of barycentres of
catenating rings with edges corresponding to the Hopf links; this net is called the Hopf ring net. The Hopf ring net approach is compared with other methods of characterizing entanglements; a number of applications of this approach to various kinds of entanglement (interpenetration, polycatenation and self-catenation) both in modelled network arrays and in coordination networks are considered
