One of the main objectives of software engineering is to develop well-structured and reliable systems. This explains the variety of approches for integrating formal and semi-formal methods ; especially those which produce B specifications from UML models. In this work, we try to unify these approaches in order to be able, on the one hand, to combine rules issued from these techniques, and on the other hand, to easily extend them. Our UML/B multi- modeling tool provides transformations from UML to B in an MDE architecture. We also proposed the notion of customizable rule which allows to adapt and extend existing approaches with respect to various abstraction levels: meta-model (M2), model (M1) or dual (M1/M2).