Framework for the Development and Testing of Dependable and Safety-Critical Systems IKTA 065/ 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 simple implementation issue –Specification faults –Software design faults –Transient (physical) faults –Permanent physical faults

The subject of the project Guaranteeing QoS 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

(Semi-)formal specification, system model (UML) Implementation Design of an IT system Mathematical model Automated model generation Analysis Mathematical analysis Back-annotation Code generation Novel approach

Visualization of dynamic sequences UML system model Implementation Design of an IT system Mathematical model Automated model generation Analysis Mathematical analysis Back-annotation Code generation Fundamental questions UML dialect (restrictions) Problem specific UML extensions Transformation semantics Proof of correctness Redundancy of the model Efficiency of the analysis Control heuristics Reversibility of the transformation

Fault simulation, Dependability analysis CTL DFN Proof of Correctness Central repository relational database XMI modelling back- annotation UML model commercial tool Model library Performability Semi-formal specification DocumentationPrototyping (simulation) Database design Object code ISO 9000 SPN Fault model, typical solutions Deductive database Transformation Rule Description (TRD) TRD 2 TRD 3 Transformation Engine Prolog XMI Planner XMI System architecture

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