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Dive into the research topics where Gerald Lüttgen is active.

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Featured researches published by Gerald Lüttgen.


applications and theory of petri nets | 2000

Efficient symbolic state-space construction for asynchronous systems

Gianfranco Ciardo; Gerald Lüttgen; Radu Siminiceanu

Many techniques for the verification of reactive systems rely on the analysis of their reachable state spaces. In this paper, a new algorithm for the symbolic generation of the state spaces of asynchronous system models, such as Petri nets, is developed. The algorithm is based on previous work that employs Multi-valued Decision Diagrams for efficiently storing sets of reachable states. In contrast to related approaches, however, it fully exploits event locality, supports intelligent cache management, and achieves faster convergence via advanced iteration control. The algorithm is implemented in the Petri net tool SMART, and runtime results show that it often performs significantly faster than existing state-space generators.


foundations of software engineering | 2000

A compositional approach to statecharts semantics

Gerald Lüttgen; Michael von der Beeck; Rance Cleaveland

Statecharts is a visual language for specifying reactive system behavior. The formalism extends traditional finite-state machines with notions of hierarchy and concurrency, and it is used in many popular software design notations. A large part of the appeal of Statecharts derives from its basis in state machines, with their intuitive operational interpretation. The classical semantics of Statecharts, however, suffers from a serious defect; it is not compositional, meaning that the behavior of system descriptions cannot be inferred from the behavior of their subsystems. Compositionality is a prerequisite for exploiting the modular structure of Statecharts for simulation, verification, and code generation, and it also provides the necessary foundation for reusability. This paper suggests a new compositional approach to formalizing Statecharts semantics as flattened labeled transition systems in which transitions represent system steps. The approach builds on ideas developed for timed process calculi and employs structural operational rules to define the transitions of a Statecharts expression in terms of the transitions of its subexpressions. It is first presented for a simple dialect of Statecharts, with respect to a variant of Pnueli and Shalevs semantics, and is illustrated by means of a small example. To demonstrate its flexibility, the proposed approach is then extended to deal with practically useful features available in many Statecharts variants, namely state references, history states, and priority concepts along state hierarchies.


international conference on concurrency theory | 1999

Statecharts Via Process Algebra

Gerald Lüttgen; Michael von der Beeck; Rance Cleaveland

Statecharts is a visual language for specifying the behavior of reactive systems. The language extends finite-state machines with concepts of hierarchy, concurrency, and priority. Despite its popularity as a design notation for embedded systems, precisely defining its semantics has proved extremely challenging. In this paper, we present a simple process algebra, called Statecharts Process Language (SPL), which is expressive enough for encoding Statecharts in a structure-preserving and semantics-preserving manner. We also establish that the behavioral equivalence bisimulation, when applied to SPL, preserves Statecharts semantics.


ACM Transactions on Computational Logic | 2002

The intuitionism behind Statecharts steps

Gerald Lüttgen; Michael Mendler

The semantics of Statecharts macro steps, as introduced by Pnueli and Shalev [1991], lacks compositionality. This article first analyzes the compositionality problem and traces it back to the invalidity of the Law of the Excluded Middle. It then characterizes the semantics via a particular class of linear intuitionistic Kripke models. This yields, for the first time in the literature, a simple fully abstract semantics that interprets Pnueli and Shalevs concept of failure naturally. The results not only give insight into the semantic subtleties of Statecharts, but also provide a basis for an implementation, for developing algebraic theories for macro steps, and for comparing different Statecharts variants.


Electronic Notes in Theoretical Computer Science | 2002

A Logical Process Calculus

Ranee Cleaveland; Gerald Lüttgen

This paper presents the Logical Process Calculus (LPC), a formalism that supports heterogeneous system specifications containing both operational and declarative subspecifications. Syntactically, LPC extends Milners Calculus of Communicating Systems with operators from the alternation-free linear-time μ-calculus (LTμ). Semantically, LPC is equipped with a behavioral preorder that generalizes Hennessys and De Nicolas must-testing preorder as well as LTμs satisfaction relation, while being compositional for all LPC operators. From a technical point of view, the new calculus is distinguished by the inclusion of (i) both minimal and maximal fixed-point operators and (ii) an unimplementability predicate on process terms which tags inconsistent specifications. The utility of LPC is demonstrated by means of an example highlighting the benefits of heterogeneous system specification.


tools and algorithms for construction and analysis of systems | 1996

Priorities for Modeling and Verifying Distributed Systems

Rance Cleaveland; Gerald Lüttgen; V. Natarajan; Steve Sims

This paper illustrates the use of priorities in process algebras by a real-world example dealing with the design of a safety-critical network which is part of a railway signaling system. Priorities in process algebras support an intuitive modeling of distributed systems since undesired inter-leavings can be suppressed. This fact also leads to a substantial reduction of the sizes of models. We have implemented a CCS-based process algebra with priorities as a new front-end for the NCSU Concurrency Workbench, and we use model checking for verifying properties of the signaling system.


Annals of Software Engineering | 1999

A practical approach to implementing real-time semantics

Girish Bhat; Rance Cleaveland; Gerald Lüttgen

This paper investigates implementations of process algebras which are suitable for modeling concurrent real-time systems. It suggests an approach for efficiently implementing real-time semantics using dynamic priorities. For this purpose a process algebra with dynamic priority is defined, whose semantics corresponds one-to-one to traditional real-time semantics. The advantage of the dynamic-priority approach is that it drastically reduces the state-space sizes of the systems in question while preserving all properties of their functional and real-time behavior. The utility of the technique is demonstrated by a case study that deals with the formal modeling and verification of several aspects of the widely-used SCSI-2 bus-protocol. The case study is carried out in the Concurrency Workbench of North Carolina, an automated verification tool in which the process algebra with dynamic priority is implemented. It turns out that the state space of the bus-protocol model is about an order of magnitude smaller than the one resulting from real-time semantics. The accuracy of the model is proved by applying model checking for verifying several mandatory properties of the bus protocol.


foundations of software technology and theoretical computer science | 2000

A Semantic Theory for Heterogeneous System Design

Rance Cleaveland; Gerald Lüttgen

This paper extends DeNicola and Hennessys testing theory from labeled transition system to Buchi processes and establishes a tight connection between the resulting Buchi must-preorder and satisfaction of linear-time temporal logic (LTL) formulas. An example dealing with the design of a communications protocol testifies to the utility of the theory for heterogeneous system design, in which some components are specified as labeled transition systems and others are given as LTL formulas.


Electronic Notes in Theoretical Computer Science | 2002

Towards a Model Theory for Esterel

Gerald Lüttgen; Michael Mendler

Abstract Esterel is a synchronous language for reactive-systems design and builds the core of the commercial tool Esterel Studio. This paper shows how the constructive semantics of a combinational fragment of Esterel, as presented by Berry, can be derived in a model-theoretic fashion, thus complementing the existing behavioral, operational, and circuit-based approaches to Esterel semantics. Technically, Esterel programs are read as formulas in propositional intuitionistic logic, which are interpreted over simple linear Kripke structures, referred to as Godel valuations. Esterel reactions are then characterized as specific Godel valuations, called response models, and it is shown that the approach is compositional in the structure of Esterel programs. The obtained results are an important step towards explaining the logic behind Esterel semantics. In addition, the intuitionistic setting advocated in this paper nicely links to Pnueli and Shalevs semantics of Harels Statecharts, another synchronous language for reactive-systems design. This offers interesting insights into the similarities of and the differences between Esterel and Statecharts semantics.


international colloquium on automata languages and programming | 2000

Fully-Abstract Statecharts Semantics via Intuitionistic Kripke Models

Gerald Lüttgen; Michael Mendler

The semantics of Statecharts macro steps, as introduced by Pnueli and Shalev, lacks compositionality. This paper first analyzes the compositionality problem and traces it back to the invalidity of the Law of the Excluded Middle. It then characterizes the semantics via a particular class of linear, intuitionistic Kripke models, namely stabilization sequences. This yields, for the first time in the literature, a simple fully-abstract semantics which interprets Pnueli and Shalevs concept of failure naturally. The results not only give insights into the semantic subtleties of Statecharts, but also provide a basis for developing algebraic theories for macro steps and for comparing different Statecharts variants.

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Radu Siminiceanu

National Institute of Aerospace

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Girish Bhat

North Carolina State University

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Steve Sims

North Carolina State University

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V. Natarajan

North Carolina State University

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