Framework for the Development and Testing of Dependable and Safety-Critical Systems IKTA 065/2000. 2001 -2003. Supported by the Information and Communication Technology Programme of the Ministry of Education
Partners • Coordinator: Budapest University of Technology and Economics, Dept. of Measurement and Information Systems • Industrial partners: – Prolan Process Control Co. – B. Braun Medical Hungary Ltd. – Magic Onyx Hungary Ltd.
Goals • Improving quality of system design by – model analysis tools and techniques for embedded and reactive systems – applied formal mathematics (hidden from the designer) • Support of standardized languages and tools – UML for visual design – off-the-shelf tools for analysis • Transfer of know-how and tools for verification
Background • Convergence of communication and information technologies – Embedded systems: Computer controlled network of intelligent sensors and actors • Convergence of the design methodologies of everyday and mission critical systems – computer systems supervised by non-professionals – fault tolerance required
Embedded systems • Long life is expected • Continuous interaction with the environment • Faults: not a simplementation issue – Specification faults – Software design faults – Transient (physical) faults – Permanent physical faults
The subject of the project • Guaranteeing Qo. S by checking and proving – completeness and consistency of the specification – correct operation of the system in presence of anticipated faults – functional correctness of control flow (dynamic behaviour)
Additional requirements • Standard languages – data exchange formats (XML) – tool independence (UML XMI) – readiness for new checking/analysis methods • ISO 9000 conform (UML-based) tools • Reuse of existing methods and tools
Novel approach Design of an IT system (Semi-)formal specification, system model (UML) Automated model generation Back-annotation Code generation Implementation Mathematical analysis Mathematical model Analysis
Fundamental questions Design of an IT system UML dialect (restrictions) Transformation semantics UML system model Problem specific UML extensions Mathematical analysis Proof of correctness Automated model generation Back-annotation Redundancy of the model Mathematical model Efficiency of the analysis Analysis Code generation Implementation Visualization of dynamic sequences Reversibility of the transformation Control heuristics
System architecture Documentation Prototyping (simulation) Semi-formal specification Database design Object code XMI CTL TRD 3 Deductive database modelling UML model commercial tool ISO 9000 Central repository XMI relational database XMI backannotation Planner SPN Fault simulation, Dependability analysis XMI Transformation Engine Prolog Performability TRD 2 ISO 9000 Fault model, typical solutions Model library XMI Proof of Correctness DFN Transformation Rule Description (TRD)
Applied analysis methods 1. Analysis of the completeness and consistency of the specification 2. Analysis of fault propagation and testability 3. Formal verification of control flow
Analysis of the specification • Safety criteria – Completeness and consistency of the semi-formal specification (UML) • Analysis techniques: – static analysis – reachability analysis (model checking) – theorem proving • Constructive methods: – design patterns (correctness proved)
Analysis of fault propagation • Extension of the model by fault effects + fault propagation • Checking the operation in the presence of expected faults • Proving coverage of fault tolerance techniques • Risk analysis
Analysis of fault propagation II. • Extended model complexity explosion • Hierarchical view: – hierarchic checking and model refinement – non-determinism • Applied formalism: Data flow networks • Proposed methods: – testability analysis (list based fault propagation) – test generation (adaptation of gate-level techniques)
Formal verification of control flow • Critical points of embedded systems: – Complex control algorithms – Event driven, asynchronous operation Exhaustive testing is not possible • Classical formal methods: – Temporal logic model checking • Proposed additional techniques: – Petri-nets + linear algebra + operation research
Expected results • Tool prototypes – completeness and consistency checker – fault proparation and testability analyzer – model verifier • Demonstration by industrial examples – functions of an artificial kidney machine – modules of a train control application • Education materials – application of the analysis tools and techniques
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