Kim Guldstrand Larsen

Uppaal in a nutshell

This paper presents the overal structure, the design criteria, and the main features of the tool box Uppaal. It gives a detailed user guide which describes how to use the various tools of Uppaal version 2.02 to construct abstract models of a real-time system, to simulate its dynamical behavior, to specify and verify its safety and bounded liveness properties in terms of its model. In addition, the paper also provides a short review on case-studies where Uppaal is applied, as well as references to its theoretical foundation.

A Tutorial on UPPAAL

This is a tutorial paper on the tool Uppaal. Its goal is to be a short introduction on the flavor of timed automata implemented in the tool, to present its interface, and to explain how to use the tool. The contribution of the paper is to provide reference examples and modeling patterns.

Bisimulation through probabilistic testing

Abstract We propose a language for testing concurrent processes and examine its strength in terms of the processes that are distinguished by a test. By using probabilistic transition systems as the underlying semantic model, we show how a testing algorithm can distinguish, with a probability arbitrarily close to one, between processes that are not bisimulation equivalent. We also show a similar result (in a slightly stronger form) for a new process relation called 2 3 - bisimulation —which lies strictly between that of simulation and bisimulation. Finally, the ultimately strength of the testing language is shown to identify a new process relation called probabilistic bisimulation—which is strictly stronger than bisimulation.

UPPAAL—a tool suite for automatic verification of real-time systems

Uppaal is a tool suite for automatic verification of safety and bounded liveness properties of real-time systems modeled as networks of timed automata. It includes: a graphical interface that supports graphical and textual representations of networks of timed automata, and automatic transformation from graphical representations to textual format, a compiler that transforms a certain class of linear hybrid systems to networks of timed automata, and a model-checker which is implemented based on constraint-solving techniques. Uppaal also supports diagnostic model-checking providing diagnostic information in case verification of a particular real-time systems fails.

A modal process logic

A novel logic is introduced for the introduction of nondeterministic and concurrent processes expressed in a process algebra. For a process algebra to be useful as a process language, it must possess compositionality, i.e. it should be possible to decompose the problem of correctness for a combined system with respect to a given specification of similar and simpler correctness problems for the components of the system. The logic presented allows such specifications to be expressed. It is an extension of process algebra in the sense that process constructs are included as connectives in the logic. Moreover, the formulas of the logic are given an operational interpretation based on which a refinement ordering between formulas is defined.<<ETX>>

Specification and refinement of probabilistic processes

A formalism for specifying probabilistic transition systems, which constitute a basic semantic model for description and analysis of, e.g. reliability aspects of concurrent and distributed systems, is presented. The formalism itself is based on transition systems. Roughly a specification has the form of a transition system in which transitions are labeled by sets of allowed probabilities. A satisfaction relation between processes and specifications that generalizes probabilistic bisimulation equivalence is defined. It is shown that it is analogous to the extension from processes to modal transition systems given by K. Larsen and B. Thomsen (1988). Another weaker criterion views a specification as defining a set of probabilistic processes; refinement is then simply containment between sets of processes. A complete method for verifying containment between specifications, which extends methods for deciding containment between specifications, which extends methods for deciding containment between finite automata or tree acceptors, is presented.<<ETX>>

On modal refinement and consistency

Almost 20 years after the original conception, we revisit several fundamental question about modal transition systems. First, we demonstrate the incompleteness of the standard modal refinement using a counterexmnple due to Huttel. Deciding any refinement, complete with respect to the standard notions of implementation, is shown to be computationally hard (co-NP hard). Second, we consider four forms of consistency (existence of implementations) ibr modal specifications. We characterize each operationally, giving algorithms for deciding, and for synthesizing implementations, together with their complexities.

Modal I/O automata for interface and product line theories

Alfaro and Henzinger use alternating simulation in a two player game as a refinement for interface automata [1]. We show that interface automata correspond to a subset of modal transition systems of Larsen and Thomsen [2], on which alternating simulation coincides with modal refinement. As a consequence a more expressive interface theory may be built, by a simple generalization from interface automata to modal automata. We define modal I/O automata, an extension of interface automata with modality. Our interface theory that follows can express liveness properties, disallowing trivial implementations of interfaces, a problem that exists for theories build around simulation preorders. In order to further exemplify the usefulness of modal I/O automata, we construct a behavioral variability theory for product line development.

Efficient on-the-fly algorithms for the analysis of timed games

In this paper, we propose the first efficient on-the-fly algorithm for solving games based on timed game automata with respect to reachability and safety properties The algorithm we propose is a symbolic extension of the on-the-fly algorithm suggested by Liu & Smolka [15] for linear-time model-checking of finite-state systems. Being on-the-fly, the symbolic algorithm may terminate long before having explored the entire state-space. Also the individual steps of the algorithm are carried out efficiently by the use of so-called zones as the underlying data structure.Various optimizations of the basic symbolic algorithm are proposed as well as methods for obtaining time-optimal winning strategies (for reachability games). Extensive evaluation of an experimental implementation of the algorithm yields very encouraging performance results.

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