This is from the original post: rule "14bisbis" salience 19 when p : Patient(p.getFumeurPetit().equals("vrai")) then //p.setHabitudesMoyennes("true"); System.out.println("14-bisbis applied: fumeurpetit->true => "+p.getFumeurPetit()); end To write a constraint against the Patient field furneurPetit you write, within a "Patient" pattern, the field name, a comparison operator and a literal, a variable or a parenthesized expression. Thus, in your case, p : Patient( fumeurPetit == "vrai" ) The proposed solution is not wrong, but less efficient and not as readable. -W On 27 October 2010 06:40, Ji Oh Yoo <jioh.yoo.dev(a)gmail.com&gt; wrote: