Drools Documentation says: Matches a field against any valid Java Regular Expression. Typically that regexp is a String, but variables that resolve to a valid regexp are also allowed. It is important to note that different from java, if you write a String regexp directly on the source file, you don't need to escape '\'. Example: but "Test\s+" is a valid RegEx (it was valid in Drools 3.x too), but now: SyntaxfehlerRule Compilation error : [Rule name=OnlineStreaming Start, agendaGroup=MAIN, salience=100, no-loop=true] com/p7s1/swi/phoenix/n24/Rule_OnlineStreaming_Start_0.java (19:923) : Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \\ ) What i'm doing wrong here? Cheers Markus