Accessing the power of distributed resources can nowadays easily be done using a middleware based on a client/server approach. Several architectures exist for those middleware's. The most scalable ones rely on a hierarchical design. Determining the best shape for the hierarchy, the one giving the best throughput of services, is not an easy task. We first propose a computation and communication model for such hierarchical middleware. Our model takes into account the deployment of several services in the hierarchy. Then, based on this model, we propose algorithms for automatically constructing a hierarchy on two kinds of heterogeneous platforms: communication homogeneous/computation heterogeneous platforms, and fully heterogeneous platforms. The proposed algorithms aim at offering the users the best obtained to requested throughput ratio, while providing fairness on this ratio for the different kinds of services, and using as few resources as possible for the hierarchy. For each kind of platforms, we compare our model with experimental results on a real middleware called DIET (Distributed Interactive Engineering Toolbox).