María Victoria Cengarle Alexander Knapp Andrzej Tarlecki Martin Wirsing A Heterogeneous Approach to UML Semantics. 383-402 2008 Concurrency, Graphs and Models http://dx.doi.org/10.1007/978-3-540-68679-8_23 conf/birthday/2008montanari db/conf/birthday/montanari2008.html#CengarleKTW08