Hi, I'm using the guvnor that comes with the jbpm-5.2.0.Final-installer-full download. I have a package in which I've created a process with condition expressions. When I build the package, I get the following error message on the Drools designer: unable to parse xml : Exception class java.lang.IllegalArgumentException : Unknown language http://www.mvel.org/2.0 My business process definintion is attached to this post. Any ideas on why this could be happening please? http://drools.46999.n3.nabble.com/file/n3786348/patientVisit.xml patientVisit.xml -- View this message in context: http://drools.46999.n3.nabble.com/Build-Error-Unknown-language-MVEL-tp378... Sent from the Drools: User forum mailing list archive at Nabble.com.