Back Propagating B System Updates on SysML/KAOS Domain Models

Nowadays, the usefulness of the formal verification and validation of system specifications is well established, at least for critical systems. However, one of the main obstacles to their adoption lies in obtaining the formal specification of the system, and, in the case of refinement-based formal methods such as B System or Event-B, in obtaining the most abstract specification that heads the development of the system. The SysML/KAOS requirements engineering method is proposed to overcome this difficulty. It includes a goal modeling language to model requirements from stakeholders needs. Translation rules from a goal model to a B System specification have already been defined. They allow to obtain a skeleton of the system specification. To complete it, a language has been defined to express the domain model associated to the goal model. Its translation gives the structural part of the B System specification. However, it very often appears that new elements must be added in the B System specification obtained from SysML/KAOS models, discovered for instance when specifying the body of events and/or by using formal validation and/or verification tools. We have therefore defined a set of rules allowing the back propagation, within domain models, of every newly added element. This paper describes these rules and how they are specified in Event-B. Their consistency is proved using the Rodin tool. We show that they are structure preserving: two related elements within the B System specification remain related within the domain model. This is done by proving various isomorphisms between the B System specification and the domain models.