Alberto Portilla Genoveva Vargas-Solar Christine Collet José-Luis Zechinelli-Martini Luciano García-Bañuelos Contract Based Behavior Model for Services Coordination. 109-123 2007 WEBIST (Selected Papers) http://dx.doi.org/10.1007/978-3-540-68262-2_9 conf/webist/2007sp db/conf/webist/webist2007sp.html#PortillaVCZG07