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Search Results: 1 - 10 of 3615 matches for " Stephan Merz "
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Event Systems and Access Control
Dominique Méry,Stephan Merz
Computer Science , 2006,
Abstract: We consider the interpretations of notions of access control (permissions, interdictions, obligations, and user rights) as run-time properties of information systems specified as event systems with fairness. We give proof rules for verifying that an access control policy is enforced in a system, and consider preservation of access control by refinement of event systems. In particular, refinement of user rights is non-trivial; we propose to combine low-level user rights and system obligations to implement high-level user rights.
Encoding TLA+ set theory into many-sorted first-order logic
Stephan Merz,Hernán Vanzetto
Computer Science , 2015,
Abstract: We present an encoding of Zermelo-Fraenkel set theory into many-sorted first-order logic, the input language of state-of-the-art SMT solvers. This translation is the main component of a back-end prover based on SMT solvers in the TLA+ Proof System.
Truly On-The-Fly LTL Model Checking
Moritz Hammer,Alexander Knapp,Stephan Merz
Computer Science , 2005,
Abstract: We propose a novel algorithm for automata-based LTL model checking that interleaves the construction of the generalized B\"{u}chi automaton for the negation of the formula and the emptiness check. Our algorithm first converts the LTL formula into a linear weak alternating automaton; configurations of the alternating automaton correspond to the locations of a generalized B\"{u}chi automaton, and a variant of Tarjan's algorithm is used to decide the existence of an accepting run of the product of the transition system and the automaton. Because we avoid an explicit construction of the B\"{u}chi automaton, our approach can yield significant improvements in runtime and memory, for large LTL formulas. The algorithm has been implemented within the SPIN model checker, and we present experimental results for some benchmark examples.
Analyzing Conflict Freedom For Multi-threaded Programs With Time Annotations
Jingshu Chen,Marie Duflot,Stephan Merz
Computer Science , 2014,
Abstract: Avoiding access conflicts is a major challenge in the design of multi-threaded programs. In the context of real-time systems, the absence of conflicts can be guaranteed by ensuring that no two potentially conflicting accesses are ever scheduled concurrently.In this paper, we analyze programs that carry time annotations specifying the time for executing each statement. We propose a technique for verifying that a multi-threaded program with time annotations is free of access conflicts. In particular, we generate constraints that reflect the possible schedules for executing the program and the required properties. We then invoke an SMT solver in order to verify that no execution gives rise to concurrent conflicting accesses. Otherwise, we obtain a trace that exhibits the access conflict.
Verifying Safety Properties With the TLA+ Proof System
Kaustuv Chaudhuri,Damien Doligez,Leslie Lamport,Stephan Merz
Computer Science , 2010, DOI: 10.1007/978-3-642-14203-1_12
Abstract: TLAPS, the TLA+ proof system, is a platform for the development and mechanical verification of TLA+ proofs written in a declarative style requiring little background beyond elementary mathematics. The language supports hierarchical and non-linear proof construction and verification, and it is independent of any verification tool or strategy. A Proof Manager uses backend verifiers such as theorem provers, proof assistants, SMT solvers, and decision procedures to check TLA+ proofs. This paper documents the first public release of TLAPS, distributed with a BSD-like license. It handles almost all the non-temporal part of TLA+ as well as the temporal reasoning needed to prove standard safety properties, in particular invariance and step simulation, but not liveness properties.
Coalescing: Syntactic Abstraction for Reasoning in First-Order Modal Logics
Damien Doligez,Jael Kriener,Leslie Lamport,Tomer Libal,Stephan Merz
Computer Science , 2014,
Abstract: We present a syntactic abstraction method to reason about first-order modal logics by using theorem provers for standard first-order logic and for propositional modal logic.
A Formalization of the Semantics of Functional-Logic Programming in Isabelle
Francisco López Fraguas,Stephan Merz,Juan Rodríguez Hortalá
Computer Science , 2009,
Abstract: Modern functional-logic programming languages like Toy or Curry feature non-strict non-deterministic functions that behave under call-time choice semantics. A standard formulation for this semantics is the CRWL logic, that specifies a proof calculus for computing the set of possible results for each expression. In this paper we present a formalization of that calculus in the Isabelle/HOL proof assistant. We have proved some basic properties of CRWL: closedness under c-substitutions, polarity and compositionality. We also discuss some insights that have been gained, such as the fact that left linearity of program rules is not needed for any of these results to hold.
A TLA+ Proof System
Kaustuv C. Chaudhuri,Damien Doligez,Leslie Lamport,Stephan Merz
Computer Science , 2008,
Abstract: We describe an extension to the TLA+ specification language with constructs for writing proofs and a proof environment, called the Proof Manager (PM), to checks those proofs. The language and the PM support the incremental development and checking of hierarchically structured proofs. The PM translates a proof into a set of independent proof obligations and calls upon a collection of back-end provers to verify them. Different provers can be used to verify different obligations. The currently supported back-ends are the tableau prover Zenon and Isabelle/TLA+, an axiomatisation of TLA+ in Isabelle/Pure. The proof obligations for a complete TLA+ proof can also be used to certify the theorem in Isabelle/TLA+.
TLA+ Proofs
Denis Cousineau,Damien Doligez,Leslie Lamport,Stephan Merz,Daniel Ricketts,Hernán Vanzetto
Computer Science , 2012,
Abstract: TLA+ is a specification language based on standard set theory and temporal logic that has constructs for hierarchical proofs. We describe how to write TLA+ proofs and check them with TLAPS, the TLA+ Proof System. We use Peterson's mutual exclusion algorithm as a simple example to describe the features of TLAPS and show how it and the Toolbox (an IDE for TLA+) help users to manage large, complex proofs.
Gen(de)red power: Die Macht des Genres im Streit um die Frauenrolle in Pastoralbriefen und Paulusakten
Annette Merz
HTS Theological Studies/Teologiese Studies , 2012, DOI: 10.4102/hts.v68i1.1185
Abstract: Gen(de)red power: The power of genre in the debate about women’s roles in the Pastoral Letters and the Acts of Paul. Two texts that contributed to the discussion on gender roles in formative Christianity, 1 Timothy and the Acts of Paul, are investigated. In both cases the emphasis is on the much-disputed role of women. Power plays a role on different levels. On the one hand power relations between the sexes are depicted or directly addressed by the text (‘gendered’ power), while on the other hand the power of persuasion is brought to bear on both male and female readers to legitimize the patriarchal, videlicet the encratitic model of gender. This is done by rhetorical means that are text-specific, but also make use of genre-specific persuasion strategies. This ‘genred power’ is still mostly unchartered territory in exegetical discussions and is therefore the focus of my investigation. Especially important in both genres are intertextual allusions to authoritative texts. Fictive self-references which enable the author (’Paul’) to correct himself are one focus of interest. Narrative strategies (i.e. character and plot development) which also have an intertextual dimension are a second focal point. The take-over of the role of Peter who denies Jesus and repents by Paul in the Acts of Thecla turns out to be of major rhetorical significance. How to cite this article: Merz, A., 2012, ‘Gen(de)red power: Die Macht des Genres im Streit um die Frauenrolle in Pastoralbriefen und Paulusakten‘, HTS Teologiese Studies/Theological Studies 68(1), #Art. 1185, 9 pages. http://dx.doi.org/10.4102/hts.v68i1.1185
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