Abderrahman Matoussi

A first attempt to combine SysML requirements diagrams and B

This article describes a work-in-progress in the framework of a research project aiming at combining requirements engineering methods with formal methods. The main idea is to extend the SysML language with concepts of existing requirements engineering methods. In this article we present extensions to SysML with concepts from the goal model of the KAOS method and we give rules to derive a formal B specification from this goal model. The approach is then illustrated on a case study.

A Goal-Based Approach to Guide the Design of an Abstract Event-B Specification

With most of formal methods, an initial formal model can be refined in multiple steps, until the final refinement contains enough details for an implementation. Most of the time, this initial model is built from the description obtained by the requirements analysis. Unfortunately, this transition from the requirements phase to the formal specification phase is one of the most painful steps and is still ambiguous. In fact, building this initial model requires a high level of competence and a lot of practice, especially as there is no well-defined process to assist designers. For that purpose, we propose a goal-based approach in which initial formal models (in Event-B) are built incrementally driven by a goal-oriented requirements engineering (GORE) paradigm.

Towards validation of requirements models

The use of formal methods for software development is escalating over the period of time. The input to this formal specification phase is often the documents obtained during the requirements analysis activity which are either textual or semi-formal. Now there is a traceability gap between analysis and specification phases as verification of the semi-formal analysis model is difficult because of poor understandability of lower level of formalism of verification tools and validation of the formal specification is difficult for customers due to their inability to understand formal models. Our objective is to bridge this gap by a gradual introduction of formalism into the requirement model in order to facilitate its validation.We analyse our requirements with KAOS (Knowledge Acquisition in autOmated Specification) [1] which is a goal-oriented methodology for requirements modeling, then we translate the KAOS goal model, following our derived precise semantics [3], into an Event-B [2] formal specification, and finally we rigourously animate the obtained specification in order to validate its conformance to original requirements with the approach defined in [4].

Specification of a localization component driven by a goal-based approach: some lessons we learned

The transition from the requirements phase to the formal specification phase is one of the most painful steps in software development. Up to now, no well-defined process to build initial formal models has been proposed. We have proposed a method in which initial formal models are built incrementally, driven by a goal-based approach. This paper aims at sharing the salient points of our experience to specify a localization component. We discuss the benefit of using a goal-based modeling to obtain an abstract Event-B specification.

Improving traceability between KAOS requirements models and b specifications

The aim of this paper is to give some feedback about the B specification [1] of a localization software component which is one of the most critical parts in the land transportation system. The main difficulties when we develop a localization component is: (i) to find the correct algorithm that merges positioning data (ii) to take into account all the properties we have to deal with. At this stage, we think that a semi formal model such as KAOS [2], a goal-based requirements engineering method, will be very useful in order to have guidelines on how to do. For that, we will just focus on the architecture of the B specifications and how using KAOS help us to build it. Since goals play an important role in requirements engineering process, rather than establishing traceability from the KAOS requirements model as a whole, we propose to establish traceability from individual goals that are part of the KAOS goal model. The main idea is to specify a correspondence rule between each concept of the goal model and B elements. Up to now, we consider only functional goals of type Achieve [2]. A B machine is associated to each goal. This machine contains an operation that “realizes” the goal; i.e. it describes the “work” to perform to reach the goal, in terms of generalized substitutions. The refinement of a goal is represented by a B refinement machine that refines the machine; the abstract operation is refined by a concrete one. This operation is built by combining operations of the machines that correspond to the sub-goals of the more abstract goal and are included in the B machine via the inclusion relationship. The nature of the combination depends on the goal refinement pattern (Milestone, AND, OR). The reader can refer to [3] for more details. The main contribution of our approach is that it establishes the first brick toward the construction of the bridge between the nonformal and the formal worlds as narrow and concise as possible. Furthermore, by discharging the proof obligations generated by the B refinement process, we can prove some properties of consistency on the goal model. Regarding the different KAOS goal model concepts, we need now to consider the translation of the concepts of domain properties and non functional goals.