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Aachen Concurrency and Dependability Week

CONCUR 2011 —— QEST 2011 —— TGC 2011

5 — 10 September 2011, Aachen, Germany.


This webpage is dedicated to the 22nd International Conference on Concurrency Theory 2011 (CONCUR 2011) and the co-located events  QEST 2011 and TGC 2011.

Information about the local organisation of all three conferences and the  accompanying workshops  can be found in due time on this web site.

For the technical aspects of QEST and TGC, please refer to their own respective web pages.

Invited Speakers

Parosh Aziz Abdulla

Parosh Aziz Abdulla (Uppsala, Sweden)

Unifying speaker with QEST 2011

Title: Probabilistic Reasoning in the Infinite World: On the Verification of Infinite-State Markov Chains
In recent years, several approaches have been proposed for automatic verification of infinite-state systems. In a parallel development, there has been an extensive research effort for the design and analysis of models with stochastic behaviors. We consider verification of Markov chains with infinite state spaces. We describe a general framework that can handle probabilistic versions of several classical models such as Petri nets, lossy channel systems, push-down automata, and noisy Turing machines. We consider both safety, liveness, and limiting behavior problems for these classes of systems. Furthermore, we describe algorithms to solve general versions of the problems in the context of stochastic games.
Slides: pdf
Rachid Guerraoui Rachid Guerraoui (EPFL Lausanne, Switzerland)
Title: Generalized Universality
Replicated state machine is a fundamental computing construct for it essentially makes a distributed system emulate a, highly available, centralized one using a consensus abstraction through which processes agree on common decisions. Any sequential object is modeled by a state machine that can be replicated over all processes of the system and accessed in a wait-free manner: we talk about the universality of the construct and of its underlying consensus abstraction. Yet, consensus is just a special case of a more general abstraction, k-set consensus, where processes agree on at most k different decisions. It is natural to ask whether there exists a generalization of state machine replication with k-set agreement, for otherwise distributed computing would not deserve the aura of having an underpinning Theory as 1 (k-set consensus with k=1) would be special. The talk will recall the classical state machine replication construct and show how, using k-set consensus as an underlying abstraction, the construct can be generalized to implement k state machines of which at least one makes progress, generalizing in a precise sense the very notion of consensus universality. (Joint work with Eli Gafni, UCLA)


Ursula Goltz Ursula Goltz (Technical University Braunschweig, Germany)
Title: On Causal Semantics of Petri Nets
We consider approaches for causal semantics of Petri nets, explicitly representing dependencies between transition occurrences. For one-safe nets or condition/event-systems, the notion of process as de- fined by Carl Adam Petri provides a notion of a run of a system where causal dependencies are reflected in terms of a partial order. A well- known problem is how to generalise this notion for nets where places may carry several tokens. Goltz and Reisig have defined such a generalisation by distinguishing tokens according to their causal history. However, this so-called individual token interpretation is often considered too detailed. A number of approaches have tackled the problem of defining a more abstract notion of process, thereby obtaining a so-called collective to- ken interpretation. Here we give a short overview on these attempts and then identify a subclass of Petri nets, called structural conflict nets, where conflict and concurrency due to token multiplicity are clearly separated. For this subclass, we define abstract processes as equivalence classes of Goltz-Reisig processes. We justify this approach by showing that we obtain exactly one maximal abstract process if and only if the underlying net is conflict-free with respect to a canonical notion of conflict. (Joint work with Rob van Glabbeek and Jens-Wolfhard Schicke)


Wil van der Aalst Wil van der Aalst (Technical University Eindhoven, The Netherlands)
Title: Discovering Concurrency: Learning Business Process Models From Examples
Process discovery - discovering a process model from example behavior recorded in an event log - is one of the most challenging tasks in process mining. Instead of analyzing the modeled behavior, one needs to learn a model based on example behaviors. It is particularly difficult to capture both concurrency and choice at the same time. This invited talk will demonstrate the importance of process mining, i.e., connecting real behavior to modeled behavior, by showing the application of this technology in a variety of organizations. Moreover, several challenges will be discussed. In particular, the talk will focus on the representational bias introduced by using a particular process notation. It will be shown that this imposes interesting new requirements on the modeling language used. See www.processmining.org and the new book on process mining (http://springer.com/978-3-642-19344-6) for more information on the topic.
Slides: pdf

Local Organisation

  • Joost-Pieter Katoen (General Chair)
  • Henrik Bohnenkamp, Arnd Gehrmann, Christina Jansen, Nils Jansen, Ulrich Loup, Thomas Noll, Elke Ohlenforst, Sabrina von Styp
  • Mathias Hülsbusch, Sander Bruggink (Workshop Chairs)

Sponsored by:

dfg_logo RWTH Aachen University Duisburg-Essen