11,513 research outputs found
Symbolic Model Checking for Dynamic Epistemic Logic
Dynamic Epistemic Logic (DEL) can model complex information
scenarios in a way that appeals to logicians. However, existing DEL
implementations are ad-hoc, so we do not know how the framework really
performs. For this purpose, we want to hook up with the best available
model-checking and SAT techniques in computational logic. We do this
by first providing a bridge: a new faithful representation of DEL models
as so-called knowledge structures that allow for symbolic model checking.
Next, we show that we can now solve well-known benchmark problems in
epistemic scenarios much faster than with existing DEL methods. Finally,
we show that our method is not just a matter of implementation, but
that it raises significant issues about logical representation and update
Symbolic Model Checking for Dynamic Epistemic Logic
Dynamic Epistemic Logic (DEL) can model complex information
scenarios in a way that appeals to logicians. However, existing DEL
implementations are ad-hoc, so we do not know how the framework really
performs. For this purpose, we want to hook up with the best available
model-checking and SAT techniques in computational logic. We do this
by first providing a bridge: a new faithful representation of DEL models
as so-called knowledge structures that allow for symbolic model checking.
Next, we show that we can now solve well-known benchmark problems in
epistemic scenarios much faster than with existing DEL methods. Finally,
we show that our method is not just a matter of implementation, but
that it raises significant issues about logical representation and update
New Directions in Model Checking Dynamic Epistemic Logic
Dynamic Epistemic Logic (DEL) can model complex information scenarios in a way that appeals to logicians. However, its existing implementations are based on explicit model checking which can only deal with small models, so we do not know how DEL performs for larger and real-world problems. For temporal logics, in contrast, symbolic model checking has been developed and successfully applied, for example in protocol and hardware verification. Symbolic model checkers for temporal logics are very efficient and can deal with very large models. In this thesis we build a bridge: new faithful representations of DEL models as so-called knowledge and belief structures that allow for symbolic model checking. For complex epistemic and factual change we introduce transformers, a symbolic replacement for action models. Besides a detailed explanation of the theory, we present SMCDEL: a Haskell implementation of symbolic model checking for DEL using Binary Decision Diagrams. Our new methods can solve well-known benchmark problems in epistemic scenarios much faster than existing methods for DEL. We also compare its performance to to existing model checkers for temporal logics and show that DEL can compete with established frameworks. We zoom in on two specific variants of DEL for concrete applications. First, we introduce Public Inspection Logic, a new framework for the knowledge of variables and its dynamics. Second, we study the dynamic gossip problem and how it can be analyzed with epistemic logic. We show that existing gossip protocols can be improved, but that no perfect strengthening of "Learn New Secrets" exists
Exploiting Asymmetry in Logic Puzzles: Using ZDDs for Symbolic Model Checking Dynamic Epistemic Logic
Binary decision diagrams (BDDs) are widely used to mitigate the
state-explosion problem in model checking. A variation of BDDs are
Zero-suppressed Decision Diagrams (ZDDs) which omit variables that must be
false, instead of omitting variables that do not matter. We use ZDDs to
symbolically encode Kripke models used in Dynamic Epistemic Logic, a framework
to reason about knowledge and information dynamics in multi-agent systems. We
compare the memory usage of different ZDD variants for three well-known
examples from the literature: the Muddy Children, the Sum and Product puzzle
and the Dining Cryptographers. Our implementation is based on the existing
model checker SMCDEL and the CUDD library. Our results show that replacing BDDs
with the right variant of ZDDs can significantly reduce memory usage. This
suggests that ZDDs are a useful tool for model checking multi-agent systems.Comment: In Proceedings TARK 2023, arXiv:2307.0400
Causality and Temporal Dependencies in the Design of Fault Management Systems
Reasoning about causes and effects naturally arises in the engineering of
safety-critical systems. A classical example is Fault Tree Analysis, a
deductive technique used for system safety assessment, whereby an undesired
state is reduced to the set of its immediate causes. The design of fault
management systems also requires reasoning on causality relationships. In
particular, a fail-operational system needs to ensure timely detection and
identification of faults, i.e. recognize the occurrence of run-time faults
through their observable effects on the system. Even more complex scenarios
arise when multiple faults are involved and may interact in subtle ways.
In this work, we propose a formal approach to fault management for complex
systems. We first introduce the notions of fault tree and minimal cut sets. We
then present a formal framework for the specification and analysis of
diagnosability, and for the design of fault detection and identification (FDI)
components. Finally, we review recent advances in fault propagation analysis,
based on the Timed Failure Propagation Graphs (TFPG) formalism.Comment: In Proceedings CREST 2017, arXiv:1710.0277
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