To combine different technology domains, modeling languages and platforms generally use a hierarchical approach. This approach avoids the combinatorial explosion of the number of interfaces between models of computation (MoC), but it for bids the use of components which have inputs or outputs that obey different MoCs. This affects the modularity and the reuse of the components. Moreover, the communication between two MoCs is implicitly defined in the modelling tool, and the designer doesnot have control over the semantics of what happens at the border between MoCs. In[7], we introduced a new approach that allows non-hierarchical heterogeneity based on heterogenous-interface components (HIC). In this paper, we present thearchitecture and the execution model we have designed to support HICs in PtolemyII.