Abstract. Synchronous languages are well suited for the design of dependable real-time systems: they enable a very high-level specification and an extremely modular implementation of complex systems by structurally decomposing them into elementary synchronous processes. To maximize the support for the generic implementation and the dynamic reconfigurability of reactive systems, we introduce a semantics of higherorder processes in a seamless extension of the synchronous language Signal. To enable the correct specification and the modular implementation of systems, we introduce an expressive type inference system for characterizing their temporal and causal invariants.