Hi there, I had something like this in drools 3.0 and it used to work but after I upgraded to drools 5.0 it doesn't work. [when]The Roof is not Type A , Type B , Type C , or RC=LM(rda != null, rda != "A", rda != "B", rda != "C", rda != "R") But to compile it now I had to make the following changes on both LHS and RHS: [when]The Roof is not Type A not Type B not Type C not RC=LM(rda != null && rda != "A" && rda != "B" && rda != "C" && rda != "R") Why does the , on the LHS doesn't compile? Thanks, Saleem