In this paper we report on an experience communicating two computer algebra systems, namely GAP (and more concretely, its HAP package to compute in Homological Algebra) and Kenzo (to compute in Algebraic Topology). Both systems cooperate through an OpenMath link in computing homology of groups. In addition, once the output from HAP has been integrated in Kenzo, it can be used to compute more complicated algebraic invariants, as homology groups of some 2-types. Categories and Subject Descriptors H.4 [Information Systems Applications]: Communications Applications; G.4 [Mathematics of Computing]: Mathematical software General Terms Homology of groups, Interoperability, OpenMath, GAP, Kenzo