86 Search Results for "Lee, David J."

Document
DOI: 10.4230/LIPIcs.DNA.30.1
Geometric Enumeration of Localized DNA Strand Displacement Reaction Networks

Authors: Matthew R. Lakin and Sarika Kumar

Published in: LIPIcs, Volume 314, 30th International Conference on DNA Computing and Molecular Programming (DNA 30) (2024)

Abstract
Localized molecular devices are a powerful tool for engineering complex information-processing circuits and molecular robots. Their practical advantages include speed and scalability of interactions between components tethered near to each other on an underlying nanostructure, and the ability to restrict interactions between more distant components. The latter is a critical feature that must be factored into computational tools for the design and simulation of localized molecular devices: unlike in solution-phase systems, the geometries of molecular interactions must be accounted for when attempting to determine the network of possible reactions in a tethered molecular system. This work aims to address that challenge by integrating, for the first time, automated approaches to analysis of molecular geometry with reaction enumeration algorithms for DNA strand displacement reaction networks that can be applied to tethered molecular systems. By adapting a simple approach to solving the biophysical constraints inherent in molecular interactions to be applicable to tethered systems, we produce a localized reaction enumeration system that enhances previous approaches to reaction enumeration in tethered system by not requiring users to explicitly specify the subsets of components that are capable of interacting. This greatly simplifies the user’s task and could also be used as the basis of future systems for automated placement or routing of signal-transmission and logical processing in molecular devices. We apply this system to several published example systems from the literature, including both tethered molecular logic systems and molecular robots.
Cite as

Matthew R. Lakin and Sarika Kumar. Geometric Enumeration of Localized DNA Strand Displacement Reaction Networks. In 30th International Conference on DNA Computing and Molecular Programming (DNA 30). Leibniz International Proceedings in Informatics (LIPIcs), Volume 314, pp. 1:1-1:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{lakin_et_al:LIPIcs.DNA.30.1,
  author =	{Lakin, Matthew R. and Kumar, Sarika},
  title =	{{Geometric Enumeration of Localized DNA Strand Displacement Reaction Networks}},
  booktitle =	{30th International Conference on DNA Computing and Molecular Programming (DNA 30)},
  pages =	{1:1--1:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-344-7},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{314},
  editor =	{Seki, Shinnosuke and Stewart, Jaimie Marie},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DNA.30.1},
  URN =		{urn:nbn:de:0030-drops-209294},
  doi =		{10.4230/LIPIcs.DNA.30.1},
  annote =	{Keywords: Localized circuits, reaction enumeration, DNA strand displacement, geometry, molecular computing}
}
Document
DOI: 10.4230/LIPIcs.DNA.30.5
Learning and Inference in a Lattice Model of Multicomponent Condensates

Authors: Cameron Chalk, Salvador Buse, Krishna Shrinivas, Arvind Murugan, and Erik Winfree

Published in: LIPIcs, Volume 314, 30th International Conference on DNA Computing and Molecular Programming (DNA 30) (2024)

Abstract
Life is chemical intelligence. What is the source of intelligent behavior in molecular systems? Here we illustrate how, in contrast to the common belief that energy use in non-equilibrium reactions is essential, the detailed balance equilibrium properties of multicomponent liquid interactions are sufficient for sophisticated information processing. Our approach derives from the classical Boltzmann machine model for probabilistic neural networks, inheriting key principles such as representing probability distributions via quadratic energy functions, clamping input variables to infer conditional probability distributions, accommodating omnidirectional computation, and learning energy parameters via a wake phase / sleep phase algorithm that performs gradient descent on the relative entropy with respect to the target distribution. While the cubic lattice model of multicomponent liquids is standard, the behaviors exhibited by the trained molecules capture both previously-observed phenomena such as core-shell condensate architectures as well as novel phenomena such as an analog of Hopfield associative memories that perform recall by contact with a patterned surface. Our final example demonstrates equilibrium classification of MNIST digits. Experimental implementation using DNA nanostar liquids is conceptually straightforward.
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Cameron Chalk, Salvador Buse, Krishna Shrinivas, Arvind Murugan, and Erik Winfree. Learning and Inference in a Lattice Model of Multicomponent Condensates. In 30th International Conference on DNA Computing and Molecular Programming (DNA 30). Leibniz International Proceedings in Informatics (LIPIcs), Volume 314, pp. 5:1-5:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{chalk_et_al:LIPIcs.DNA.30.5,
  author =	{Chalk, Cameron and Buse, Salvador and Shrinivas, Krishna and Murugan, Arvind and Winfree, Erik},
  title =	{{Learning and Inference in a Lattice Model of Multicomponent Condensates}},
  booktitle =	{30th International Conference on DNA Computing and Molecular Programming (DNA 30)},
  pages =	{5:1--5:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-344-7},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{314},
  editor =	{Seki, Shinnosuke and Stewart, Jaimie Marie},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.DNA.30.5},
  URN =		{urn:nbn:de:0030-drops-209330},
  doi =		{10.4230/LIPIcs.DNA.30.5},
  annote =	{Keywords: multicomponent liquid, Boltzmann machine, phase separation}
}
Document
DOI: 10.4230/LIPIcs.COSIT.2024.7
What Is a Spatio-Temporal Model Good For?: Validity as a Function of Purpose and the Questions Answered by a Model

Authors: Simon Scheider and Judith A. Verstegen

Published in: LIPIcs, Volume 315, 16th International Conference on Spatial Information Theory (COSIT 2024)

Abstract
The concept of validity is a cornerstone of science. Given this central role, it is somewhat surprising to find that validity remains a rather obscure concept. Unfortunately, the term is often reduced to a matter of ground truth data, seemingly because we fail to come to grips with it. In this paper, instead, we take a purpose-based approach to the validity of spatio-temporal models. We argue that a model application is valid only if the model delivers an answer to a particular spatio-temporal question specifying some experiment including spatio-temporal controls and measures. Such questions constitute the information purposes of models, forming an intermediate layer in a pragmatic knowledge pyramid with corresponding levels of validity. We introduce a corresponding question-based grammar that allows us to formally distinguish among contemporary inference, prediction, retrodiction, projection, and retrojection models. We apply the grammar to corresponding examples and discuss the possibilities for validating such models as a means to a given end.
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Simon Scheider and Judith A. Verstegen. What Is a Spatio-Temporal Model Good For?: Validity as a Function of Purpose and the Questions Answered by a Model. In 16th International Conference on Spatial Information Theory (COSIT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 315, pp. 7:1-7:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{scheider_et_al:LIPIcs.COSIT.2024.7,
  author =	{Scheider, Simon and Verstegen, Judith A.},
  title =	{{What Is a Spatio-Temporal Model Good For?: Validity as a Function of Purpose and the Questions Answered by a Model}},
  booktitle =	{16th International Conference on Spatial Information Theory (COSIT 2024)},
  pages =	{7:1--7:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-330-0},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{315},
  editor =	{Adams, Benjamin and Griffin, Amy L. and Scheider, Simon and McKenzie, Grant},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.COSIT.2024.7},
  URN =		{urn:nbn:de:0030-drops-208225},
  doi =		{10.4230/LIPIcs.COSIT.2024.7},
  annote =	{Keywords: validity, fitness-for-purpose, spatio-temporal modeling, pragmatics, question grammar}
}
Document
DOI: 10.4230/LIPIcs.ITP.2024.9
Verifying Peephole Rewriting in SSA Compiler IRs

Authors: Siddharth Bhat, Alex Keizer, Chris Hughes, Andrés Goens, and Tobias Grosser

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract
There is an increasing need for domain-specific reasoning in modern compilers. This has fueled the use of tailored intermediate representations (IRs) based on static single assignment (SSA), like in the MLIR compiler framework. Interactive theorem provers (ITPs) provide strong guarantees for the end-to-end verification of compilers (e.g., CompCert). However, modern compilers and their IRs evolve at a rate that makes proof engineering alongside them prohibitively expensive. Nevertheless, well-scoped push-button automated verification tools such as the Alive peephole verifier for LLVM-IR gained recognition in domains where SMT solvers offer efficient (semi) decision procedures. In this paper, we aim to combine the convenience of automation with the versatility of ITPs for verifying peephole rewrites across domain-specific IRs. We formalize a core calculus for SSA-based IRs that is generic over the IR and covers so-called regions (nested scoping used by many domain-specific IRs in the MLIR ecosystem). Our mechanization in the Lean proof assistant provides a user-friendly frontend for translating MLIR syntax into our calculus. We provide scaffolding for defining and verifying peephole rewrites, offering tactics to eliminate the abstraction overhead of our SSA calculus. We prove correctness theorems about peephole rewriting, as well as two classical program transformations. To evaluate our framework, we consider three use cases from the MLIR ecosystem that cover different levels of abstractions: (1) bitvector rewrites from LLVM, (2) structured control flow, and (3) fully homomorphic encryption. We envision that our mechanization provides a foundation for formally verified rewrites on new domain-specific IRs.
Cite as

Siddharth Bhat, Alex Keizer, Chris Hughes, Andrés Goens, and Tobias Grosser. Verifying Peephole Rewriting in SSA Compiler IRs. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 9:1-9:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bhat_et_al:LIPIcs.ITP.2024.9,
  author =	{Bhat, Siddharth and Keizer, Alex and Hughes, Chris and Goens, Andr\'{e}s and Grosser, Tobias},
  title =	{{Verifying Peephole Rewriting in SSA Compiler IRs}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{9:1--9:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.9},
  URN =		{urn:nbn:de:0030-drops-207372},
  doi =		{10.4230/LIPIcs.ITP.2024.9},
  annote =	{Keywords: compilers, semantics, mechanization, MLIR, SSA, regions, peephole rewrites}
}
Document
DOI: 10.4230/LIPIcs.ITP.2024.13
Completeness of Asynchronous Session Tree Subtyping in Coq

Authors: Burak Ekici and Nobuko Yoshida

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract
Multiparty session types (MPST) serve as a foundational framework for formally specifying and verifying message passing protocols. Asynchronous subtyping in MPST allows for typing optimised programs preserving type safety and deadlock freedom under asynchronous interactions where the message order is preserved and sending is non-blocking. The optimisation is obtained by message reordering, which allows for sending messages earlier or receiving them later. Sound subtyping algorithms have been extensively studied and implemented as part of various programming languages and tools including C, Rust and C-MPI. However, formalising all such permutations under sequencing, selection, branching and recursion in session types is an intricate task. Additionally, checking asynchronous subtyping has been proven to be undecidable. This paper introduces the first formalisation of asynchronous subtyping in MPST within the Coq proof assistant. We first decompose session types into session trees that do not involve branching and selection, and then establish a coinductive refinement relation over them to govern subtyping. To showcase our formalisation, we prove example subtyping schemas that appear in the literature, all of which cannot be verified, at the same time, by any of the existing decidable sound algorithms. Additionally, we take the (inductive) negation of the refinement relation from a prior work by Ghilezan et al. [Ghilezan et al., 2023] and re-implement it, significantly reducing the number of rules (from eighteen to eight). We establish the completeness of subtyping with respect to its negation in Coq, addressing the issues concerning the negation rules outlined in the previous work [Ghilezan et al., 2023]. In the formalisation, we use the greatest fixed point of the least fixed point technique, facilitated by the paco library, to define coinductive predicates. We employ parametrised coinduction to prove their properties. The formalisation consists of roughly 10K lines of Coq code, accessible at: https://github.com/ekiciburak/sessionTreeST/tree/itp2024.
Cite as

Burak Ekici and Nobuko Yoshida. Completeness of Asynchronous Session Tree Subtyping in Coq. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 13:1-13:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{ekici_et_al:LIPIcs.ITP.2024.13,
  author =	{Ekici, Burak and Yoshida, Nobuko},
  title =	{{Completeness of Asynchronous Session Tree Subtyping in Coq}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{13:1--13:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.13},
  URN =		{urn:nbn:de:0030-drops-207418},
  doi =		{10.4230/LIPIcs.ITP.2024.13},
  annote =	{Keywords: asynchronous multiparty session types, session trees, subtyping, Coq}
}
Document
DOI: 10.4230/LIPIcs.ITP.2024.19
Modular Verification of Intrusive List and Tree Data Structures in Separation Logic

Authors: Marc Hermes and Robbert Krebbers

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract
Intrusive linked data structures are commonly used in low-level programming languages such as C for efficiency and to enable a form of generic types. Notably, intrusive versions of linked lists and search trees are used in the Linux kernel and the Boost C++ library. These data structures differ from ordinary data structures in the way that nodes contain only the meta data (i.e. pointers to other nodes), but not the data itself. Instead the programmer needs to embed nodes into the data, thereby avoiding pointer indirections, and allowing data to be part of several data structures. In this paper we address the challenge of specifying and verifying intrusive data structures using separation logic. We aim for modular verification, where we first specify and verify the operations on the nodes (without the data) and then use these specifications to verify clients that attach data. We achieve this by employing a representation predicate that separates the data structure’s node structure from the data that is attached to it. We apply our methodology to singly-linked lists - from which we build cyclic and doubly-linked lists - and binary trees - from which we build binary search trees. All verifications are conducted using the Coq proof assistant, making use of the Iris framework for separation logic.
Cite as

Marc Hermes and Robbert Krebbers. Modular Verification of Intrusive List and Tree Data Structures in Separation Logic. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 19:1-19:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{hermes_et_al:LIPIcs.ITP.2024.19,
  author =	{Hermes, Marc and Krebbers, Robbert},
  title =	{{Modular Verification of Intrusive List and Tree Data Structures in Separation Logic}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{19:1--19:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.19},
  URN =		{urn:nbn:de:0030-drops-207478},
  doi =		{10.4230/LIPIcs.ITP.2024.19},
  annote =	{Keywords: Separation Logic, Program Verification, Data Structures, Iris, Coq}
}
Document
DOI: 10.4230/LIPIcs.ITP.2024.30
A Coq Formalization of Taylor Models and Power Series for Solving Ordinary Differential Equations

Authors: Sewon Park and Holger Thies

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract
In exact real computation real numbers are manipulated exactly without round-off errors, making it well-suited for high precision verified computation. In recent work we propose an axiomatic formalization of exact real computation in the Coq theorem prover. The formalization admits an extended extraction mechanism that lets us extract computational content from constructive parts of proofs to efficient programs built on top of AERN, a Haskell library for exact real computation. Many processes in science and engineering are modeled by ordinary differential equations (ODEs), and often safety-critical applications depend on computing their solutions correctly. The primary goal of the current work is to extend our framework to spaces of functions and to support computation of solutions to ODEs and other essential operators. In numerical mathematics, the most common way to represent continuous functions is to use polynomial approximations. This can be modeled by so-called Taylor models, that encode a function as a polynomial and a rigorous error-bound over some domain. We define types of classical functions that do not hold any computational content and formalize Taylor models to computationally approximate those classical functions. Classical functions are defined in a way to admit classical principles in their constructions and verification. We define various basic operations on Taylor models and verify their correctness based on the classical functions that they approximate. We then shift our interest to analytic functions as a generalization of Taylor models where polynomials are replaced by infinite power series. We use the formalization to develop a theory of non-linear polynomial ODEs. From the proofs we can extract certified exact real computation programs that compute solutions of ODEs on some time interval up to any precision.
Cite as

Sewon Park and Holger Thies. A Coq Formalization of Taylor Models and Power Series for Solving Ordinary Differential Equations. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 30:1-30:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{park_et_al:LIPIcs.ITP.2024.30,
  author =	{Park, Sewon and Thies, Holger},
  title =	{{A Coq Formalization of Taylor Models and Power Series for Solving Ordinary Differential Equations}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{30:1--30:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.30},
  URN =		{urn:nbn:de:0030-drops-207581},
  doi =		{10.4230/LIPIcs.ITP.2024.30},
  annote =	{Keywords: Exact real computation, Taylor models, Analytic functions, Computable analysis, Program extraction}
}
Document
DOI: 10.4230/LIPIcs.ITP.2024.36
Defining and Preserving More C Behaviors: Verified Compilation Using a Concrete Memory Model

Authors: Andrew Tolmach, Chris Chhak, and Sean Anderson

Published in: LIPIcs, Volume 309, 15th International Conference on Interactive Theorem Proving (ITP 2024)

Abstract
We propose a concrete ("pointer as integer") memory semantics for C that supports verified compilation to a target environment having simple "public vs. private" data protection based on tagging or sandboxing (such as the WebAssembly virtual machine). Our semantics gives definition to a range of legacy programming idioms that cause undefined behavior in standard C, and are not covered by existing verified compilers, but that often work in practice. Compiler correctness in this context implies that target programs are secure against all control-flow attacks (although not against data-only attacks). To avoid tying our semantics too closely to particular compiler implementation choices, it is parameterized by a novel form of oracle that non-deterministically chooses the addresses of stack and heap allocations. As a proof-of-concept, we formalize a small RTL-like language and verify two-way refinement for a compiler from this language to a low-level machine and runtime system with hardware tagging. Our Coq formalization and proofs are provided as supplementary material.
Cite as

Andrew Tolmach, Chris Chhak, and Sean Anderson. Defining and Preserving More C Behaviors: Verified Compilation Using a Concrete Memory Model. In 15th International Conference on Interactive Theorem Proving (ITP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 309, pp. 36:1-36:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{tolmach_et_al:LIPIcs.ITP.2024.36,
  author =	{Tolmach, Andrew and Chhak, Chris and Anderson, Sean},
  title =	{{Defining and Preserving More C Behaviors: Verified Compilation Using a Concrete Memory Model}},
  booktitle =	{15th International Conference on Interactive Theorem Proving (ITP 2024)},
  pages =	{36:1--36:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-337-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{309},
  editor =	{Bertot, Yves and Kutsia, Temur and Norrish, Michael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITP.2024.36},
  URN =		{urn:nbn:de:0030-drops-207643},
  doi =		{10.4230/LIPIcs.ITP.2024.36},
  annote =	{Keywords: Compiler verification, C language semantics, Coq proof assistant}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.7
Fairness and Consensus in an Asynchronous Opinion Model for Social Networks

Authors: Jesús Aranda, Sebastián Betancourt, Juan Fco. Díaz, and Frank Valencia

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
We introduce a DeGroot-based model for opinion dynamics in social networks. A community of agents is represented as a weighted directed graph whose edges indicate how much agents influence one another. The model is formalized using labeled transition systems, henceforth called opinion transition systems (OTS), whose states represent the agents' opinions and whose actions are the edges of the influence graph. If a transition labeled (i,j) is performed, agent j updates their opinion taking into account the opinion of agent i and the influence i has over j. We study (convergence to) opinion consensus among the agents of strongly-connected graphs with influence values in the interval (0,1). We show that consensus cannot be guaranteed under the standard strong fairness assumption on transition systems. We derive that consensus is guaranteed under a stronger notion from the literature of concurrent systems; bounded fairness. We argue that bounded-fairness is too strong of a notion for consensus as it almost surely rules out random runs and it is not a constructive liveness property. We introduce a weaker fairness notion, called m-bounded fairness, and show that it guarantees consensus. The new notion includes almost surely all random runs and it is a constructive liveness property. Finally, we consider OTS with dynamic influence and show convergence to consensus holds under m-bounded fairness if the influence changes within a fixed interval [L,U] with 0 < L < U < 1. We illustrate OTS with examples and simulations, offering insights into opinion formation under fairness and dynamic influence.
Cite as

Jesús Aranda, Sebastián Betancourt, Juan Fco. Díaz, and Frank Valencia. Fairness and Consensus in an Asynchronous Opinion Model for Social Networks. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 7:1-7:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{aranda_et_al:LIPIcs.CONCUR.2024.7,
  author =	{Aranda, Jes\'{u}s and Betancourt, Sebasti\'{a}n and D{\'\i}az, Juan Fco. and Valencia, Frank},
  title =	{{Fairness and Consensus in an Asynchronous Opinion Model for Social Networks}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{7:1--7:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.7},
  URN =		{urn:nbn:de:0030-drops-207794},
  doi =		{10.4230/LIPIcs.CONCUR.2024.7},
  annote =	{Keywords: Social networks, fairness, DeGroot, consensus, asynchrony}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.9
Risk-Averse Optimization of Total Rewards in Markovian Models Using Deviation Measures

Authors: Christel Baier, Jakob Piribauer, and Maximilian Starke

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
This paper addresses objectives tailored to the risk-averse optimization of accumulated rewards in Markov decision processes (MDPs). The studied objectives require maximizing the expected value of the accumulated rewards minus a penalty factor times a deviation measure of the resulting distribution of rewards. Using the variance in this penalty mechanism leads to the variance-penalized expectation (VPE) for which it is known that optimal schedulers have to minimize future expected rewards when a high amount of rewards has been accumulated. This behavior is undesirable as risk-averse behavior should keep the probability of particularly low outcomes low, but not discourage the accumulation of additional rewards on already good executions. The paper investigates the semi-variance, which only takes outcomes below the expected value into account, the mean absolute deviation (MAD), and the semi-MAD as alternative deviation measures. Furthermore, a penalty mechanism that penalizes outcomes below a fixed threshold is studied. For all of these objectives, the properties of optimal schedulers are specified and in particular the question whether these objectives overcome the problem observed for the VPE is answered. Further, the resulting algorithmic problems on MDPs and Markov chains are investigated.
Cite as

Christel Baier, Jakob Piribauer, and Maximilian Starke. Risk-Averse Optimization of Total Rewards in Markovian Models Using Deviation Measures. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 9:1-9:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{baier_et_al:LIPIcs.CONCUR.2024.9,
  author =	{Baier, Christel and Piribauer, Jakob and Starke, Maximilian},
  title =	{{Risk-Averse Optimization of Total Rewards in Markovian Models Using Deviation Measures}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{9:1--9:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.9},
  URN =		{urn:nbn:de:0030-drops-207816},
  doi =		{10.4230/LIPIcs.CONCUR.2024.9},
  annote =	{Keywords: Markov decision processes, risk-aversion, deviation measures, total reward}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.13
The Power of Counting Steps in Quantitative Games

Authors: Sougata Bose, Rasmus Ibsen-Jensen, David Purser, Patrick Totzke, and Pierre Vandenhove

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
We study deterministic games of infinite duration played on graphs and focus on the strategy complexity of quantitative objectives. Such games are known to admit optimal memoryless strategies over finite graphs, but require infinite-memory strategies in general over infinite graphs. We provide new lower and upper bounds for the strategy complexity of mean-payoff and total-payoff objectives over infinite graphs, focusing on whether step-counter strategies (sometimes called Markov strategies) suffice to implement winning strategies. In particular, we show that over finitely branching arenas, three variants of limsup mean-payoff and total-payoff objectives admit winning strategies that are based either on a step counter or on a step counter and an additional bit of memory. Conversely, we show that for certain liminf total-payoff objectives, strategies resorting to a step counter and finite memory are not sufficient. For step-counter strategies, this settles the case of all classical quantitative objectives up to the second level of the Borel hierarchy.
Cite as

Sougata Bose, Rasmus Ibsen-Jensen, David Purser, Patrick Totzke, and Pierre Vandenhove. The Power of Counting Steps in Quantitative Games. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 13:1-13:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{bose_et_al:LIPIcs.CONCUR.2024.13,
  author =	{Bose, Sougata and Ibsen-Jensen, Rasmus and Purser, David and Totzke, Patrick and Vandenhove, Pierre},
  title =	{{The Power of Counting Steps in Quantitative Games}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{13:1--13:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.13},
  URN =		{urn:nbn:de:0030-drops-207852},
  doi =		{10.4230/LIPIcs.CONCUR.2024.13},
  annote =	{Keywords: Games on graphs, Markov strategies, quantitative objectives, infinite-state systems}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.15
RobTL: Robustness Temporal Logic for CPS

Authors: Valentina Castiglioni, Michele Loreti, and Simone Tini

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
We propose Robustness Temporal Logic (RobTL), a novel temporal logic for the specification and analysis of distances between the behaviours of Cyber-Physical Systems (CPS) over a finite time horizon. RobTL specifications allow us to measure the differences in the behaviours of systems with respect to various objectives and temporal constraints, and to study how those differences evolve in time. Specifically, the unique features of RobTL allow us to specify robustness properties of CPS against uncertainty and perturbations. As an example, we use RobTL to analyse the robustness of an engine system that is subject to attacks aimed at inflicting overstress of equipment.
Cite as

Valentina Castiglioni, Michele Loreti, and Simone Tini. RobTL: Robustness Temporal Logic for CPS. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 15:1-15:23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{castiglioni_et_al:LIPIcs.CONCUR.2024.15,
  author =	{Castiglioni, Valentina and Loreti, Michele and Tini, Simone},
  title =	{{RobTL: Robustness Temporal Logic for CPS}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{15:1--15:23},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.15},
  URN =		{urn:nbn:de:0030-drops-207870},
  doi =		{10.4230/LIPIcs.CONCUR.2024.15},
  annote =	{Keywords: Cyber-physical systems, robustness, temporal logic, uncertainty}
}
Document
DOI: 10.4230/LIPIcs.CONCUR.2024.40
A PSPACE Algorithm for Almost-Sure Rabin Objectives in Multi-Environment MDPs

Authors: Marnix Suilen, Marck van der Vegt, and Sebastian Junges

Published in: LIPIcs, Volume 311, 35th International Conference on Concurrency Theory (CONCUR 2024)

Abstract
Markov Decision Processes (MDPs) model systems with uncertain transition dynamics. Multiple-environment MDPs (MEMDPs) extend MDPs. They intuitively reflect finite sets of MDPs that share the same state and action spaces but differ in the transition dynamics. The key objective in MEMDPs is to find a single strategy that satisfies a given objective in every associated MDP. The main result of this paper is PSPACE-completeness for almost-sure Rabin objectives in MEMDPs. This result clarifies the complexity landscape for MEMDPs and contrasts with results for the more general class of partially observable MDPs (POMDPs), where almost-sure reachability is already EXP-complete, and almost-sure Rabin objectives are undecidable.
Cite as

Marnix Suilen, Marck van der Vegt, and Sebastian Junges. A PSPACE Algorithm for Almost-Sure Rabin Objectives in Multi-Environment MDPs. In 35th International Conference on Concurrency Theory (CONCUR 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 311, pp. 40:1-40:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{suilen_et_al:LIPIcs.CONCUR.2024.40,
  author =	{Suilen, Marnix and van der Vegt, Marck and Junges, Sebastian},
  title =	{{A PSPACE Algorithm for Almost-Sure Rabin Objectives in Multi-Environment MDPs}},
  booktitle =	{35th International Conference on Concurrency Theory (CONCUR 2024)},
  pages =	{40:1--40:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-339-3},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{311},
  editor =	{Majumdar, Rupak and Silva, Alexandra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CONCUR.2024.40},
  URN =		{urn:nbn:de:0030-drops-208120},
  doi =		{10.4230/LIPIcs.CONCUR.2024.40},
  annote =	{Keywords: Markov Decision Processes, partial observability, linear-time Objectives}
}
Document
DOI: 10.4230/LIPIcs.CP.2024.9
Pseudo-Boolean Reasoning About States and Transitions to Certify Dynamic Programming and Decision Diagram Algorithms

Authors: Emir Demirović, Ciaran McCreesh, Matthew J. McIlree, Jakob Nordström, Andy Oertel, and Konstantin Sidorov

Published in: LIPIcs, Volume 307, 30th International Conference on Principles and Practice of Constraint Programming (CP 2024)

Abstract
Pseudo-Boolean proof logging has been used successfully to provide certificates of optimality from a variety of constraint- and satisifability-style solvers that combine reasoning with a backtracking or clause-learning search. Another paradigm, occurring in dynamic programming and decision diagram solving, instead reasons about partial states and possible transitions between them. We describe a framework for generating clean and efficient pseudo-Boolean proofs for these kinds of algorithm, and use it to produce certifying algorithms for knapsack, longest path, and interval scheduling. Because we use a common proof system, we can also reason about hybrid solving algorithms: we demonstrate this by providing proof logging for a dynamic programming based knapsack propagator inside a constraint programming solver.
Cite as

Emir Demirović, Ciaran McCreesh, Matthew J. McIlree, Jakob Nordström, Andy Oertel, and Konstantin Sidorov. Pseudo-Boolean Reasoning About States and Transitions to Certify Dynamic Programming and Decision Diagram Algorithms. In 30th International Conference on Principles and Practice of Constraint Programming (CP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 307, pp. 9:1-9:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{demirovic_et_al:LIPIcs.CP.2024.9,
  author =	{Demirovi\'{c}, Emir and McCreesh, Ciaran and McIlree, Matthew J. and Nordstr\"{o}m, Jakob and Oertel, Andy and Sidorov, Konstantin},
  title =	{{Pseudo-Boolean Reasoning About States and Transitions to Certify Dynamic Programming and Decision Diagram Algorithms}},
  booktitle =	{30th International Conference on Principles and Practice of Constraint Programming (CP 2024)},
  pages =	{9:1--9:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-336-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{307},
  editor =	{Shaw, Paul},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CP.2024.9},
  URN =		{urn:nbn:de:0030-drops-206948},
  doi =		{10.4230/LIPIcs.CP.2024.9},
  annote =	{Keywords: Proof logging, dynamic programming, decision diagrams}
}
Document
DOI: 10.4230/LIPIcs.CP.2024.12
Using Constraint Programming for Disjunctive Scheduling in Temporal AI Planning

Authors: Adam Francis Green, J. Christopher Beck, and Amanda Coles

Published in: LIPIcs, Volume 307, 30th International Conference on Principles and Practice of Constraint Programming (CP 2024)

Abstract
We present a novel scheduling model that leverages Constraint Programming (CP) to enhance problem solving performance in Temporal Planning. Building on the established strategy of decomposing causal and temporal reasoning, our approach abstracts two common fact structures present in many Temporal Planning problems - Semaphores and Envelopes - and performs temporal reasoning in a CP-based scheduler. At each search node in a heuristic search for a temporal plan, we construct and solve a Constraint Satisfaction Problem (CSP) and integrate feedback from the CP-based scheduler to guide the causal planning search towards a solution. Through experimental analysis, we validate the impact of these advances, demonstrating a significant reduction in both the number of states searched and in search time alongside an increase in problem-solving coverage.
Cite as

Adam Francis Green, J. Christopher Beck, and Amanda Coles. Using Constraint Programming for Disjunctive Scheduling in Temporal AI Planning. In 30th International Conference on Principles and Practice of Constraint Programming (CP 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 307, pp. 12:1-12:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

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@InProceedings{francisgreen_et_al:LIPIcs.CP.2024.12,
  author =	{Francis Green, Adam and Beck, J. Christopher and Coles, Amanda},
  title =	{{Using Constraint Programming for Disjunctive Scheduling in Temporal AI Planning}},
  booktitle =	{30th International Conference on Principles and Practice of Constraint Programming (CP 2024)},
  pages =	{12:1--12:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-336-2},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{307},
  editor =	{Shaw, Paul},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CP.2024.12},
  URN =		{urn:nbn:de:0030-drops-206974},
  doi =		{10.4230/LIPIcs.CP.2024.12},
  annote =	{Keywords: AI Planning, Temporal-Numeric Planning, Constraint Programming, Scheduling}
}
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