A partial order semantics approach to the clock explosion problem of timed automata

AbstractWe present a new approach to the symbolic model checking of timed automata based on a partial order semantics. It relies on event zones that use vectors of event occurrences instead of clock zones that use vectors of clock values grouped in polyhedral clock constraints. We provide a description of the different congruences that arise when we consider an independence relation in a timed framework. We introduce a new abstraction, called catchup equivalence which is defined on event zones and which can be seen as an implementation of one of the (more abstract) previous congruences. This formal language approach helps clarifying what the issues are and which properties abstractions should have. The catchup equivalence yields an algorithm to check emptiness which has the same complexity bound in the worst case as the algorithm to test emptiness in the classical semantics of timed automata. Our approach works for the class of timed automata proposed by Alur–Dill, except for state invariants (an extension including state invariants is discussed informally). First experiments show that the approach is promising and may yield very significant improvements

Search-based system architecture development using a holistic modeling approach

This dissertation presents an innovative approach to system architecting where search algorithms are used to explore design trade space for good architecture alternatives. Such an approach is achieved by integrating certain model construction, alternative generation, simulation, and assessment processes into a coherent and automated framework. This framework is facilitated by a holistic modeling approach that combines the capabilities of Object Process Methodology (OPM), Colored Petri Net (CPN), and feature model. The resultant holistic model can not only capture the structural, behavioral, and dynamic aspects of a system, allowing simulation and strong analysis methods to be applied, it can also specify the architectural design space. Both object-oriented analysis and design (OOA/D) and domain engineering were exploited to capture design variables and their domains and define architecture generation operations. A fully realized framework (with genetic algorithms as the search algorithm) was developed. Both the proposed framework and its suggested implementation, including the proposed holistic modeling approach and architecture alternative generation operations, are generic. They are targeted at systems that can be specified using object-oriented or process-oriented paradigm. The broad applicability of the proposed approach is demonstrated on two examples. One is the configuration of reconfigurable manufacturing systems (RMSs) under multi-objective optimization and the other is the architecture design of a manned lunar landing system for the Apollo program. The test results show that the proposed approach can cover a huge number of architecture alternatives and support the assessment of several performance measures. A set of quality results was obtained after running the optimization algorithm following the proposed framework --Abstract, page iii

Ninth Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools, Aarhus, Denmark, October 20-22, 2008

This booklet contains the proceedings of the Ninth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 20-22, 2008. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop0

Coping with the State Explosion Problem in Formal Methods: Advanced Abstraction Techniques and Big Data Approaches.

Formal verification of dynamic, concurrent and real-time systems has been the focus of several decades of software engineering research. Formal verification requires high-performance data processing software for extracting knowledge from the unprecedented amount of data containing all reachable states and all transitions that systems can make among those states, for instance, the extraction of specific reachable states, traces, and more. One of the most challenging task in this context is the development of tools able to cope with the complexity of real-world models analysis. Many methods have been proposed to alleviate this problem. For instance, advanced state space techniques aim at reducing the data needed to be constructed in order to verify certain properties. Other directions are the efficient implementation of such analysis techniques, and studying ways to parallelize the algorithms in order to exploit multi-core and distributed architectures. Since cloud-based computing resources have became easily accessible, there is an opportunity for verification techniques and tools to undergo a deep technological transition to exploit the new available architectures. This has created an increasing interest in parallelizing and distributing verification techniques. Cloud computing is an emerging and evolving paradigm where challenges and opportunities allow for new research directions and applications. There is an evidence that this trend will continue, in fact several companies are putting remarkable efforts in delivering services able to offer hundreds, or even thousands, commodity computers available to customers, thus enabling users to run massively parallel jobs. This revolution is already started in different scientific fields, achieving remarkable breakthroughs through new kinds of experiments that would have been impossible only few years ago. Anyway, despite many years of work in the area of multi-core and distributed model checking, still few works introduce algorithms that can scale effortlessly to the use of thousands of loosely connected computers in a network, so existing technology does not yet allow us to take full advantage of the vast array of compute power of a "cloud" environment. Moreover, despite model checking software tools are so called "push-button", managing a high-performance computing environment required by distributed scientific applications, is far from being considered such, especially whenever one wants to exploit general purpose cloud computing facilities. The thesis focuses on two complementary approaches to deal with the state explosion problem in formal verification. On the one hand we try to decrease the exploration space by studying advanced state space methods for real-time systems modeled with Time Basic Petri nets. In particular, we addressed and solved several different open problems for such a modeling formalism. On the other hand, we try to increase the computational power by introducing approaches, techniques and software tools that allow us to leverage the "big data" trend to some extent. In particular, we provided frameworks and software tools that can be easily specialized to deal with the construction and verification of very huge state spaces of different kinds of formalisms by exploiting big data approaches and cloud computing infrastructures

Seventh Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools, Aarhus, Denmark, October 24-26, 2006

This booklet contains the proceedings of the Seventh Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 24-26, 2006. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop0

Fifth Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools Aarhus, Denmark, October 8-11, 2004

This booklet contains the proceedings of the Fifth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 8-11, 2004. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop0

Sixth Workshop and Tutorial on Practical Use of Coloured Petri Nets and the CPN Tools Aarhus, Denmark, October 24-26, 2005

This booklet contains the proceedings of the Sixth Workshop on Practical Use of Coloured Petri Nets and the CPN Tools, October 24-26, 2005. The workshop is organised by the CPN group at the Department of Computer Science, University of Aarhus, Denmark. The papers are also available in electronic form via the web pages: http://www.daimi.au.dk/CPnets/workshop0

An Intelligent Transportation System to control air pollution and road traffic in cities ntegrating CEP and Colored Petri Nets

Air pollution generated by road traffic in large cities is a great concern in today’s society since pollution has an important impact on human health, even causing premature deaths. To address the problem, this paper presents an Intelligent Transportation System model based on Complex Event Processing technology and Colored Petri Nets (CPNs). It takes into consideration the levels of environmental pollution and road traffic, according to the air quality levels accepted by the international recommendations as well as the handbook emission factors for road transport methodology. This proposal, therefore, tackles a common problem in today’s large cities, where traffic restrictions must be applied due to environmental pollution. CPNs are used in this work as a tool to make decisions about traffic regulations, so as to reduce pollution levels

Conformance testing : measuring the alignment between event logs and process models

Many companies have adopted Process Aware Information Systems (PAIS) for supporting their business processes in some form. On the one hand these systems typically log events (e.g., in transaction logs or audit trails) related to the actual business process executions. On the other hand explicit process models describing how the business process should (or is expected to) be executed are frequently available. Together with the data recorded in the log, this raises the interesting question "Do the model and the log conform to each other?". Conformance testing, also referred to as conformance analysis, aims at the detection of inconsistencies between a process model and its corresponding execution log, and their quantification by the formation of metrics. This paper proposes an incremental approach to check the conformance of a process model and an event log. At first, the fitness between the log and the model is ensured (i.e., "Does the observed process comply with the control flow specified by the process model?"). At second, the appropriateness of the model can be analyzed with respect to the log (i.e., "Does the model describe the observed process in a suitable way?"). Furthermore, this suitability must be evaluated from both a structural and a behavioral perspective. To verify the presented ideas a Conformance Checker has been implemented within the ProM framewor