Sari Leppänen

Formal service-oriented development of fault tolerant communicating systems

Telecommunication systems should have a high degree of availability, i.e., high probability of correct and timely provision of requested services. To achieve this, correctness of software for such systems and system fault tolerance should be ensured. Application of formal methods helps us to gain confidence in building correct software. However, to be used in practice, formal methods should be well integrated into existing development process. In this paper we propose a formal model-driven approach to development of communicating systems. Essentially our approach formalizes and extends Lyra – a top-down service-oriented method for development of communicating systems. Lyra is based on transformation and decomposition of models expressed in UML2. We formalize Lyra in the B Method by proposing a set of formal specification and refinement patterns reflecting the essential models and transformations of the Lyra service specification, decomposition and distribution phases. Moreover, we extend Lyra to integrate reasoning about fault tolerance in the entire development flow.

Verifying Reliable Data Transmission over UMTS Radio Interface with High Level Petri Nets

Standard specifications of telecommunication protocols are mainly written using informal language. Therefore testing the standard, i.e. the definition of the core functionality, requires formal modelling of the protocol. In this article we describe the modelling and verification of a third generation mobile telecommunication protocol. We take the SDL description of the protocol as a starting point for our High Level Petri Net model. Since the size of the real-life protocols is enormous, we apply various abstraction techniques in the modelling phase. Basing on these and our previous experience, we introduce several heuristics for intelligent protocol modelling. Next we describe in detail the verification and modelling task, and derivation of the properties to be verified from the protocol specification. We are able to verify the most essential properties for reliable data transmission. Before executing the actual verification task, we plan a verification strategy, where for example the verification order of the properties and the appropriate configurations for the protocol and channel components for each run are considered.

Formal Verification of Consistency in Model-Driven Development of Distributed Communicating Systems and Communication Protocols

Currently UML2 is widely used for modelling software-intensive systems. Model driven development of complex software typically starts from abstract, high-level UML2 models which specify the system from several different viewpoints. Abstract models are further refined into more detailed design models in successive development stages. While specifying various aspects and abstraction levels of such systems, we create a set of different models, which should be inter- and intra-consistent. In this paper we propose an approach to ensuring consistency in Lyra - a rigorous, service-oriented and model-based method for developing industrial telecommunication systems and communication protocols. We derive informal requirements to ensuring intra- and inter- consistency and then formalize them in the B method. The formalization in B allows us to structure complex informal requirements and formally ensure intra- and inter-consistency of models created at various stages of the Lyra development.

Formal model-driven development of communicating systems

Telecommunicating systems should have a high degree of availability, i.e., high probability of correct and timely provision of requested services. To achieve this, correctness of software for such systems should be ensured. Application of formal methods helps us to gain confidence in building correct software. However, to be used in practice, the formal methods should be well integrated into existing development process. In this paper we propose a formal model-driven approach to development of communicating systems. Essentially our approach formalizes Lyra – a top-down service-oriented method for development of communicating systems. Lyra is based on transformation and decomposition of models expressed in UML2. We formalize Lyra in the B Method by proposing a set of formal specification and refinement patterns reflecting the essential models and transformations of Lyra. The proposed approach is illustrated by a case study.

Formal Reasoning about Fault Tolerance and Parallelism in Communicating Systems

Telecommunication systems should have a high degree of availability, i.e., high probability of correct provision of requested services. To achieve this, correctness of software for such systems and system fault tolerance should be ensured. In our previous work we proposed an approach to formalisation and extension of Lyra --- a top-down service-oriented method for development of communicating systems. Lyra is based on transformation and decomposition of models expressed in UML2. We formalised Lyra in the B Method by proposing a set of formal specification and refinement patterns reflecting the essential Lyra models and transformations. At the same time, we also focused on integration of fault tolerance mechanisms into the entire Lyra development flow. In this paper, we extend our Lyra formalisation to model parallel execution of services. This significantly increases both complexity and flexibility of the presented models.

A modelling method for rigorous and automated design of large-scale industrial systems

Compositional architecture-driven and model-based system design holds huge potential to increase design efficiency and improve design quality for large-scale industrial systems. Transition to such design paradigm is hampered by the lack of domain-specific methods and tools that give adequate support for both behavioral and structural modeling and development automation. This paper introduces an enhancement to Lyra, a rigorous service-oriented modeling method for the design of communicating distributed systems that brings process algebraic thinking into industrial system specification with particular focus on behavior. This enhancement offers a sound basis for implementing the ideas of MDA in automation of system design, functional verification and conformance testing. The Lyra method and its enhancement are exemplified using UML2 to model a critical and complex part of the mobile WiMAX wireless system.

Service-Oriented Development of Fault Tolerant Communicating Systems: Refinement Approach

Telecommunication systems must have a high degree of availability, that is, a high probability of correct and timely provision of requested services. To achieve this, correctness of software for such systems should be ensured. Application of formal methods helps increase confidence in building correct software. However, to be used in practice, formal methods should be well integrated into existing development process. In this paper, the authors propose a formal model-driven approach to development of communicating systems. The authors formalize and extend the Lyra approach-a top-down service-oriented method for development of communicating systems. Lyra is based on transformation and decomposition of models expressed in UML2. The authors formalize Lyra in the B Method by proposing a set of formal specification and refinement patterns reflecting the essential models and transformations of the Lyra phases. Moreover, this paper extends Lyra to integrate reasoning about fault tolerance in the entire development flow.

A Case Study: Applying Lyra in Modeling S60 Camera Functionality

We present an application of a modeling method for distributed systems to a case study of mobile phone camera functionality based on an existing implementation. The modeling method, Lyra, utilizes formal definitions, in this case UML2 state machines, for behavior We observe the industrial application of the models, for instance modeling conventions and tool support needed to enable it, and the application cases of model based testing and illustration of system properties