statecharts and categories

Dear Categoricians, I'm wondering if there has been any work in formalizing statecharts [1] in categorical terms. If not, do you know of an other algebraic description of this specification language? Also, it seems to me that the operationnal semantic STATEMATE of Statecharts as described in [2] is very coalgebraic in nature. Did anybody write something about this? Thank you for any information or pointer, Matthieu REFERENCES: [1] Harel, D. (1987) Statecharts: A visual formalism for complex systems. Science of Computer Programming, 8(3), 231--274. [2] Harel, D. and Naamad, A. (1996) The STATEMATE Semantics of Statecharts. ACM Transactions on Software Engineering and Methodology, 5(4), 293--333