  In model based development, embedded systems are modeled using a mix of
dataflow formalism, that capture the flow of computation, and hierarchical
state machines, that capture the modal behavior of the system. For safety
analysis, existing approaches rely on a compilation scheme that transform the
original model (dataflow and state machines) into a pure dataflow formalism.
Such compilation often result in loss of important structural information that
capture the modal behaviour of the system. In previous work we have developed a
compilation technique from a dataflow formalism into modular Horn clauses. In
this paper, we present a novel technique that faithfully compile hierarchical
state machines into modular Horn clauses. Our compilation technique preserves
the structural and modal behavior of the system, making the safety analysis of
such models more tractable.
