Lars G Johansson

Bio: Lars G Johansson is an academic researcher. The author has contributed to research in topics: Formal verification & Verification. The author has an hindex of 1, co-authored 1 publications receiving 3 citations.

Formal Verification of UML-RT Capsules using Model Checking

Abstract: Formal verification methods have successfully been used to ensure correctness of both hardware and software systems. In contrast to testing methods, that can demonstrate the presence of faults in a system, formal methods can prove their absence. A department of the telecommunications company Ericsson AB in Gothenburg, Sweden, uses the UML-RT language to model software used in WCDMA radio base stations. These concurrent and reactive systems can be modeled in the Eclipse-based RSARTE environment. Previous work underlines a need of narrowing the gap between software development tools used in industry and formal verification tools. This thesis examines the feasibility of using model checking to verify properties of UMLRT capsules. We present a prototype tool for generating verification models in the Promela language for the model checker Spin. The tool is implemented as a model-to-text transformation using the JET tool and is integrated into RSARTE. The result of the work establishes that it, for a subset of constructs in UML-RT, is possible to automate generation of verification models that can be used to demonstrate properties of the original UML-RT capsules. We demonstrate this with example models created in RSARTE.

Formalizing non-concurrent UML state machines using colored petri nets

Abstract: UML state machines are an interesting graphical language to express dynamic systems behavior. However, using the different features available (hierarchy, internal/external transitions, entry/exit/do activities, history pseudostates, etc.) may yield quite complex behaviors that are difficult to inspect and check visually. We introduce an algorithm to automatically generate a colored Petri net model associated with a state machine description, so as to provide a formal specification. In this proposal, although we do not consider concurrent aspects (such as fork and join), we take into ac- count all the above mentioned features in a thorough and integrated way. This is illustrated on some examples.

Formalising concurrent UML state machines using coloured Petri nets

Abstract: With the increasing complexity of dynamic concurrent systems, a phase of formal specification and formal verification is needed. UML state machines are widely used to specify dynamic systems behaviours. However, the official semantics of UML is described in a semi-formal manner, which renders the formal verification of complex systems delicate. In this paper, we propose a formalisation of UML state machines using coloured Petri nets. We consider in particular concurrent aspects (orthogonal regions, forks, joins, variables), the hierarchy induced by composite states and their associated activities, external, local or inter-level transitions, entry/exit/do behaviours, transition priorities, and shallow history pseudostates. We use a CD player as a motivating example, and run various verifications using CPN Tools.

Refactoring Guidelines for a UML-RT based Software System.

Abstract: A large software system is not a static product that can be planned, implemented and then forgotten when finished Software systems are rather evolving entities that need continuous maintenance and refactoring to improve their structure This is a large and common problem in the software industry, as products age they accumulate more features and large amounts of code that the initial architecture were not designed for This leads to a fragmented code base and a slower development processOvercoming software complexity can not be directly solved by a single solution As the problem itself is not caused by a single issue or property, it rather consists of multiple issues that in combination cause the larger problem This thesis goes through some of the problems that where found in a large software system at Ericsson and different types of solutions that might improve the overall structure and development efficiency of the systemThe direction of this thesis has been to introduce development guidelines into the development of the system at Ericsson The main goal of these guidelines is to decrease the need to do large refactorings and instead focus on more frequent and smaller refactorings The guidelines touch on different areas of the development to improve the structure and the development efficiency of the system The areas that are mainly focused on are the architecture, the visual UML diagrams and the source code The main recommendations that have been concluded are the importance of using modern and iterative development processes that include refactoring as an integral part of its phases and to use a more extensible architecture for the system itself As these recommendations are part of a long term solution they are complemented by guidelines for the more daily development to improve the current source code from getting fragmented