Petur Olsen

Automata Learning Through Counterexample-Guided Abstraction Refinement

Abstraction is the key when learning behavioral models of realistic systems. Hence, in most practical applications where automata learning is used to construct models of software components, researchers manually define abstractions which, depending on the history, map a large set of concrete events to a small set of abstract events that can be handled by automata learning tools. In this article, we show how such abstractions can be constructed fully automatically for a restricted class of extended finite state machines in which one can test for equality of data parameters, but no operations on data are allowed. Our approach uses counterexample-guided abstraction refinement: whenever the current abstraction is too coarse and induces nondeterministic behavior, the abstraction is refined automatically. Using Tomte, a prototype tool implementing our algorithm, we have succeeded to learn – fully automatically – models of several realistic software components, including the biometric passport and the SIP protocol.

Model-based schedulability analysis of safety critical hard real-time Java programs

In this paper, we present a novel approach to schedulability analysis of Safety Critical Hard Real-Time Java programs. The approach is based on a translation of programs, written in the Safety Critical Java profile introduced in [21] for the Java Optimized Processor [18], to timed automata models verifiable by the Uppaal model checker [23]. Schedulability analysis is reduced to a simple reachability question, checking for deadlock freedom. Model-based schedulability analysis has been developed by Amnell et al. [2], but has so far only been applied to high level specifications, not actual implementations in a programming language. Experiments show that model-based schedulability analysis can result in a more accurate analysis than possible with traditional approaches, thus systems deemed non-schedulable by traditional approaches may in fact be schedulable, as detected by our analysis. Our approach has been implemented in a tool, named SARTS, successfully used to verify the schedulability of a real-time sorting machine consisting of two periodic and two sporadic tasks. SARTS has also been applied on a number of smaller examples to investigate properties of our approach.

HomePort: Middleware for heterogeneous home automation networks

Ambient Intelligence systems use many sensors and actuators, with a diversity of networks, protocols and technologies which makes it impossible to access the devices in a common manner. This paper presents the HomePort software, which provides an open source RESTful interface to heterogeneous sensor networks, allowing a simple unified access to virtually any kind of protocol using well known standards. HomePort includes means to provide event notification, as well as a tracing mechanism. The software is implemented and we report on initial experiments and provide an evaluation that shows the feasibility and scalability of the approach.

opaal: a lattice model checker

We present a new open source model checker, opaal, for automatic verification of models using lattice automata. Lattice automata allow the users to incorporate abstractions of a model into the model itself. This provides an efficient verification procedure, while giving the user fine-grained control of the level of abstraction by using a method similar to Counter-Example Guided Abstraction Refinement. The opaal engine supports a subset of the UPPAAL timed automata language extended with lattice features. We report on the status of the first public release of opaal, and demonstrate how opaal can be used for efficient verification on examples from domains such as database programs, lossy communication protocols and cache analysis.

Formal Analysis and Testing of Real-Time Automotive Systems Using UPPAAL Tools

Many safety-concerned standards and regulations for real-time embedded systems, e.g., ISO 26262 for automotive electric/electronic systems, recommends the use of formal techniques to achieve the required safety level. This paper presents a method for formal analysis of real-time embedded systems. The method allows properties to be statistically checked early and quickly with high confidence, and may also produce a formal proof when required. This environment exploits uppaal tools consisting of a symbolic model checker (uppaal MC) and a statistical model checker (uppaal smc), and a model-based testing environment (uppaal Yggdrasil), all of which are based on a formal model in timed automata. We demonstrate our method on an industrial case, an automotive Turn Indicator System, showing how the design of the system at the early phase of system development may be efficiently checked against the defined system requirements.

A Toolchain for Home Automation Controller Development

Home Automation systems provide a large number of devices to control diverse appliances. Taking advantage of this diversity to create efficient and intelligent environments requires well designed, validated, and implemented controllers. However, designing and deploying such controllers is a complex and error prone process. This paper presents a tool chain that transforms a design in the form of communicating state machines to an executable controller that interfaces to appliances through a service oriented middleware. Design and validation is supported by integrated model checking and simulation facilities. This is extendable to controller synthesis. This tool chain is implemented, and we provide different examples to show its usability.

Present and Absent Sets: Abstraction for Testing of Reactive Systems with Databases

We present a new abstraction of reactive systems interacting with databases. This abstraction is intended to be used for model-based testing. We abstract the database into two sets: present set and absent set, and present a proof of this abstraction. We present two extensions of FSM, the DBFSM and PAFSM. DBFSM are a form of FSM incorporating databases. PAFSM are an abstraction of DBFSM using present-absent sets. Depending on what type of testing is to be done, the translation is tailored to fit this purpose. We show how this translation is related to the present-absent abstraction. Finally, we illustrate the approach through a small example and show how this can be used for testing with the model-based testing tool Uppaal TRON.

Model-based testing of industrial transformational systems

We present an approach for modeling and testing transformational systems in an industrial context. The systems are modeled as a set of boolean formulas. Each formula is called a clause and is an expression for an expected output value. To manage complexities of the models, we employ a modeling trick for handling dependencies, by using some output values from the system under test to verify other output values. To avoid circular dependencies, the clauses are arranged in a hierarchy, where each clause depends on the outputs of its children. This modeling trick enables us to model and test complex systems, using relatively simple models. Pairwise testing is used for test case generation. This manages the number of test cases for complex systems. The approach is developed based on a case study for testing printer controllers in professional printers at Oce. The model-based testing approach results in increased maintainability and gives better understanding of test cases and their produced output. Using pairwise testing resulted in measurable coverage, with a test set smaller than the manually created test set. To illustrate the applicability of the approach, we show how the approach can be used to model and test parts of a controller for ventilation in livestock stables.

Toolchain for user-centered intelligent floor heating control

Floor heating systems are important components of nowadays home-automation setups. The control of a floor heating system is a nontrivial task and the present solutions essentially implement variants of a simple bang-bang controller that opens for a hot water circulation in a room if its current temperature is below the user defined target temperature, otherwise it closes for the heating in the room. The disadvantage is that the heat exchange among the rooms, outside weather conditions, weather forecast and other factors are not considered. We propose a novel model-driven approach for intelligent floor heating control based on a chain of tools that allow us to gather the sensor readings from the actual hardware and use the state-of-the-art controller synthesis tool UPPAAL Stratego in order to synthesise abstract control strategies that are then executed on the real hardware platform provided by the company Seluxit. We have built a scaled demonstrator of the system and the experimental results document a 38% to 52 % increase in user satisfaction, moreover with additional energy savings between 2% to 12%.

An Energy Flexibility Framework on The Internet of Things

This paper presents a framework for management of flexible energy loads in the context of the Internet of Things and the Smart Grid. The framework takes place in the European project Arrowhead, and aims at taking advantage of the flexibility (in time and power) of energy production and consumption offered by sets of devices, appliances or buildings, to help at solving the issue of fluctuating energy production of renewable energies. The underlying concepts are explained, the actors involved in the framework, their incentives and interactions are detailed, and a technical overview is provided. An implementation of the framework is presented, as well as the expected results of the pilots.