GCSR: A Graphical Language With Algebraic Semantics for the Specification of Real-Time Systems

Graphical Communicating Shared Resources, GCSR, is a formal language for specifying real-time systems including their functional and resource requirements. A GCSR specification consists of a set of nodes that are connected with directed, labeled edges, which describe possible execution flows. Nodes represent instantaneous selection among execution flows, or time and resource consuming system activities. In addition, a node can represent a system subcomponent, which allows modular, hierarchical, thus scalable system specifications. Edges are labeled with instantaneous communication actions or time to describe the duration of activities in the source node. GCSR supports the explicit representation of resources and priorities to resolve resource contention. The semantics of GCSR is the Algebra of Communicating Shared Resources, a timed process algebra with operational semantics that makes GCSR specifications executable. Furthermore, the process algebra provides behavioral equivalence relations between GCSR specifications. These equivalence relations can be used to replace a GCSR specification with an equivalent specification inside another, and to minimize a GCSR specification in terms of the number of nodes and edges. The paper defines the GCSR language, describes GCSR specification reductions that preserve the specification behaviors, and illustrates GCSR with example design specifications

Automatic generation of SDL specifications from timed MSCs

The integration of Formal Description Techniques (FDTs) in the software process enables formal validation, translation, synthesis and code generation. Message Sequence Charts (MSC) and Specification and Description Language (SDL) are two formal languages, widely used in the telecommunication industry. Generally MSC is used for the behavioral requirement specification, while SDL is used for the detailed design specification. The transition from the requirement specification to the design specification is usually performed manually; and the design has to be validated against the requirement specification. In a previous research work, researchers from the telesoft group at Concordia University devised an approach for generating SDL specifications from MSC specifications with a given target architecture. It guarantees correctness of the design, and consistency between the SDL specification and the MSC specification. The need for validation has been eliminated. Time concepts have been introduced in MSC-2000, which enables real-time requirements to be specified in MSC. Building on the existing framework, this thesis presents a new approach for translating MSCs with real-time requirements into SDL specifications. We analyzed and classified different types of time constraints and measurements. New algorithms for analyzing MSC specifications and generating SDL code were devised. We also built the tool and experimented with case studies to prove the feasibility of our approach

From UML to AADL: a Need for an Explicit Execution Semantics Modeling with MARTE

International audienceA modeling process for real-time embedded systems may involve the coordinated use of several languages. Each of these languages are dedicated to a particular phase of development (specification, design, test, ...) and coupled with various tools (scheduling analysis, formal verification, model checker,...). The combined use of UML and AADL is an increasing practice. UML and its recent MARTE (Modeling and Analysis of Real-Time and Embedded systems) profile seem suitable for capturing requirements, analysis and preliminary design. AADL is tailored for the detailed design phase and offers linked validation and verification tools. In order to combine UML/MARTE and AADL, translation mechanisms between these two formalisms have to be defined. Previous works have defined translations between the structural concepts of AADL and MARTE artifacts. However, the behavioral aspect have also to be treated. The presented work focuses on the translation of the thread execution and communication semantics. It is a pragmatic and on-going approach, validated in an industrial context, on representative examples

Completeness, robustness, and safety in real-time software requirements specification

This paper presents an approach to providing a rigorous basis for ascertaining whether or not a given set of software requirements is internally complete, i.e., closed with respect to questions and inferences that can be made on the basis of information included in the specification. Emphasis is placed on aspects of software requirements specifications that previously have not been adequately handled, including timing abstractions, safety, and robustness

Contracts and Behavioral Patterns for SoS: The EU IP DANSE approach

This paper presents some of the results of the first year of DANSE, one of the first EU IP projects dedicated to SoS. Concretely, we offer a tool chain that allows to specify SoS and SoS requirements at high level, and analyse them using powerful toolsets coming from the formal verification area. At the high level, we use UPDM, the system model provided by the british army as well as a new type of contract based on behavioral patterns. At low level, we rely on a powerful simulation toolset combined with recent advances from the area of statistical model checking. The approach has been applied to a case study developed at EADS Innovation Works.Comment: In Proceedings AiSoS 2013, arXiv:1311.319

Transformation of UML Behavioral Diagrams to Support Software Model Checking

Unified Modeling Language (UML) is currently accepted as the standard for modeling (object-oriented) software, and its use is increasing in the aerospace industry. Verification and Validation of complex software developed according to UML is not trivial due to complexity of the software itself, and the several different UML models/diagrams that can be used to model behavior and structure of the software. This paper presents an approach to transform up to three different UML behavioral diagrams (sequence, behavioral state machines, and activity) into a single Transition System to support Model Checking of software developed in accordance with UML. In our approach, properties are formalized based on use case descriptions. The transformation is done for the NuSMV model checker, but we see the possibility in using other model checkers, such as SPIN. The main contribution of our work is the transformation of a non-formal language (UML) to a formal language (language of the NuSMV model checker) towards a greater adoption in practice of formal methods in software development.Comment: In Proceedings FESCA 2014, arXiv:1404.043

A Contract-Based Methodology for Aircraft Electric Power System Design

In an aircraft electric power system, one or more supervisory control units actuate a set of electromechanical switches to dynamically distribute power from generators to loads, while satisfying safety, reliability, and real-time performance requirements. To reduce expensive redesign steps, this control problem is generally addressed by minor incremental changes on top of consolidated solutions. A more systematic approach is hindered by a lack of rigorous design methodologies that allow estimating the impact of earlier design decisions on the final implementation. To achieve an optimal implementation that satisfies a set of requirements, we propose a platform-based methodology for electric power system design, which enables independent implementation of system topology (i.e., interconnection among elements) and control protocol by using a compositional approach. In our flow, design space exploration is carried out as a sequence of refinement steps from the initial specification toward a final implementation by mapping higher level behavioral and performance models into a set of either existing or virtual library components at the lower level of abstraction. Specifications are first expressed using the formalisms of linear temporal logic, signal temporal logic, and arithmetic constraints on Boolean variables. To reason about different requirements, we use specialized analysis and synthesis frameworks and formulate assume guarantee contracts at the articulation points in the design flow. We show the effectiveness of our approach on a proof-of-concept electric power system design