Hi there, ok so which version of jBPM and Drools are you using?
This class was in the drools-compiler.jar or in the drools-core.jar so make sure that you have all the required dependencies into your web application..
Cheers
PS: el foro es en ingles y por lo general recomiendo que se escriba en ingles asi mucha mas gente te puede ayudar. Saludos!