Martijn Hendriks

UPPAAL 4.0

UPPAAL 4.0 is the result of over two and a half years of development and contains many new features, additions to the modeling language, performance improvements, enhancements and polish to the easy to use graphical user interface, and is accompanied by several open source libraries. The tool and libraries are available free of charge for academic, educational and evaluation purposes from http://www.uppaal.com/. We describe three of the new features: user defined functions, priorities and symmetry reduction

Adding Symmetry Reduction to Uppaal

We describe a prototype extension of the real-time model checking tool Uppaal with symmetry reduction. The symmetric data type scalarset, which is also used in the Murϕ model checker, was added to Uppaal’s system description language to support the easy static detection of symmetries. Our prototype tool uses state swaps, described and proven sound earlier by Hendriks, to reduce the space and memory consumption of Uppaal. Moreover, the reduction strategy is canonical, which means that the symmetries are optimally used. For all examples that we experimented with (both academic toy examples and industrial cases), we obtained a drastic reduction of both computation time and memory usage, exponential in the size of the scalar sets used.

Model-driven design-space exploration for embedded systems: the octopus toolset

The complexity of todays embedded systems and their development trajectories requires a systematic, model-driven design approach, supported by tooling wherever possible. Only then, development trajectories become manageable, with high-quality, cost-effective results. This paper introduces the Octopus Design-Space Exploration (DSE) toolset that aims to leverage existing modeling, analysis, and DSE tools to support model-driven DSE for embedded systems. The current toolset integrates Uppaal and CPN Tools, and is centered around the DSE Intermediate Representation (DSEIR) that is specifically designed to support DSE. The toolset architecture allows: (i) easy reuse of models between different tools, while providing model consistency, and the combined use of these tools in DSE; (ii) domain-specific abstractions to support different application domains and easy reuse of tools across domains.

Exact Acceleration of Real-Time Model Checking

Dierent time scales do often occur in real-time systems, e.g., a polling real-time system samples the environment many times per second, whereas the environment may only change a few times per second. When these systems are modeled as (networks of) timed automata, the validation using symbolic model checking techniques can significantly be slowed down by unnecessary fragmentation of the symbolic state space. This paper introduces a syntactical adjustment to a subset of timed automata that addresses this fragmentation problem and that can speed-up forward symbolic reachability analysis in a significant way. We prove that this syntactical adjustment does not alter reachability properties and that it indeed is eective. We illustrate our exact acceleration technique with run-time data obtained with the model checkers Uppaal and Kronos. Moreover, we demonstrate that automated application of our exact acceleration technique can significantly speed-up the verification of the run-time behavior of LEGO Mindstorms programs.

Production scheduling by reachability analysis - a case study

Schedule synthesis based on reachability analysis of timed automata has received attention in the last few years. The main strength of this approach is that the expressiveness of timed automata allows - unlike many classical approaches - the modelling of scheduling problems of very different kinds. Furthermore, the models are robust against changes in the parameter setting and against changes in the problem specification. This paper presents a case study that was provided by Axxom, an industrial partner of the AMETIST project. It consists of a scheduling problem for lacquer production, and is treated with the timed automata approach. A number of problems have to be addressed for the modelling task: the information transfer from the industrial partner, the derivation of timed automaton model for the case study, and the heuristics that have to be added in order to reduce the search space. We try to isolate the generic problems of modelling for model checking, and suggest solutions that are also applicable for other scheduling cases. Model checking experiments and solutions are discussed.

Model checking the time to reach agreement

The timed automaton framework of Alur and Dill is a natural choice for the specification of partially synchronous distributed systems (systems which have only partial information about timing, e.g., only an upper bound on the message delay). The past has shown that verification of these systems by model checking usually is very difficult. The present paper demonstrates that an agreement algorithm of Attiya et al, which falls into a – for model checkers – particularly problematic subclass of partially synchronous distributed systems, can easily be modeled with the Uppaal model checker, and that it is possible to analyze some interesting and non-trivial instances with reasonable computational resources. Although existing techniques are used, this is an interesting case study in its own right that adds to the existing body of experience. Furthermore, the agreement algorithm has not been formally verified before to the author’s knowledge.

Model checker aided design of a controller for a wafer scanner

For a case-study of a wafer scanner from the semiconductor industry it is shown how model checking techniques can be used to compute (1) a simple yet optimal deadlock avoidance policy, and (2) an infinite schedule that optimizes throughput. in the absence of errors. Deadlock avoidance is studied based on a simple finite state model using Smv, and for throughput analysis a more detailed timed automaton model has been constructed and analyzed using the Uppaal tool. The Smv and Uppaal models are formally related through the notion of a stuttering bisimulation. The results were obtained within 2 weeks, which confirms once more that model checking techniques may help to improve the design process of realistic, industrial systems. Methodologically, the case study is interesting since two models were used to obtain results that could not have been obtained using only a single model.

Integrated model-driven design-space exploration for embedded systems

Embedded systems and their design trajectories are becoming increasingly complex, and there is a growing demand for performance, reliability, energy efficiency and low cost. To cope with these challenges, decision making early in the development trajectory needs to be supported by appropriate modeling and analysis. To achieve this support, we need to find the modeling abstractions that allow extensive design-space exploration, tune these modeling abstractions towards the users, and integrate support for different types of modeling and analysis.

Scheduling lacquer production by reachability analysis - A case study

In this paper we describe a case study on lacquer production scheduling that was performed in the European IST-project AMETIST and was provided by one of the industrial partners. The approach is to derive schedules by means of reachability analysis: with this technique the search mechanism of model checkers, in our case here Uppaal, is used to find feasible or optimal schedules. The advantage of this approach is that the expressiveness of timed automata allows to model scheduling problems of different kinds, unlike many classical approaches, and the problem class is robust against changes in the parameter setting. To fight the typical state space explosion problem a number of standard heuristics have to be used. We discuss the difficulties when modelling an industrial case of this kind, describe the experiments we performed, the heuristics used, and the techniques applied to allow to optimize costs (storage costs, delay costs, etc.) while searching for schedules.

Architecture for self-organizing, co-operative and robust Building Automation Systems

This paper provides an overview of the architecture for self-organizing, co-operative and robust Building Automation Systems (BAS) proposed by the EC funded FP7 SCUBA1 project. We describe the current situation in monitoring and control systems and outline the typical stakeholders involved in the case of building automation systems. We derive seven typical use cases which will be demonstrated and evaluated on pilot sites. From these use cases the project designed an architecture relying on six main modules that realize the design, commissioning and operation of self-organizing, co-operative, robust BAS.