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Boosting answer set Optimization with Weighted Comparator Networks

THEORY AND PRACTICE OF LOGIC programming 2020年第4期20卷 512-551页

作者： Bomanson, Jori Janhunen, Tomi Aalto Univ Dept Comp Sci FI-00076 Aalto Finland Tampere Univ Informat Technol & Commun Sci FI-33014 Tampere Finland

answer set programming (ASP) is a paradigm for modeling knowledge-intensive domains and solving challenging reasoning problems. In ASP solving, a typical strategy is to preprocess problem instances by rewriting complex rules into simpler ones. Normalization is a rewriting process that removes extended rule types altogether in favor of normal rules. Recently, such techniques led to optimization rewriting in ASP, where the goal is to boost answer set optimization by refactoring the optimization criteria of interest. In this paper, we present a novel, general, and effective technique for optimization rewriting based on comparator networks which are specific kinds of circuits for reordering the elements of vectors. The idea is to connect an ASP encoding of a comparator network to the literals being optimized and to redistribute the weights of these literals over the structure of the network. The encoding captures information about the weight of an answer set in auxiliary atoms in a structured way that is proven to yield exponential improvements during branch-and-bound optimization on an infinite family of example programs. The used comparator network can be tuned freely, for example, to find the best size for a given benchmark class. Experiments show accelerated optimization performance on several benchmark problems.

关键词： answer set programming comparator network normalization optimization rewriting translation

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New models for generating hard random boolean formulas and disjunctive logic programs

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ARTIFICIAL INTELLIGENCE 2020年 279卷

作者： Amendola, Giovanni Ricca, Francesco Truszczynski, Miroslaw Univ Calabria Dept Math & Comp Sci Commenda Di Rende Italy Univ Kentucky Dept Comp Sci Lexington KY 40506 USA

We propose two models of random quantified boolean formulas and their natural random disjunctive logic program counterparts. The models extend the standard models of random k-CNF formulas and the Chen-Interian model of random 2QBFs. The first model controls the generation of programs and QSAT formulas by imposing a specific structure on rules and clauses, respectively. The second model is based on a family of QSAT formulas in a non-clausal form. We provide theoretical bounds for the phase transition region in our models, and show experimentally the presence of the easy-hard-easy pattern and its alignment with the location of the phase transition. We show that boolean formulas and logic programs from our models are significantly harder than those obtained from the standard k-CNF and Chen-Interian models, and that their combination yields formulas and programs that are "super-hard" to evaluate. We also provide evidence suggesting that formulas from one of our models are well suited for assessing solvers tuned to real-world instances. Finally, it is noteworthy that, to the best of our knowledge, our models and results on random disjunctive logic programs are the first of their kind. (C) 2019 Elsevier B.V. All rights reserved.

关键词： answer set programming Random boolean formulas Phase transition Random logic programs

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The External Interface for Extending WASP

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THEORY AND PRACTICE OF LOGIC programming 2020年第2期20卷 225-248页

作者： Dodaro, Carmine Ricca, Francesco Univ Genoa DIBRIS Genoa Italy Univ Calabria DEMACS Arcavacata Di Rende Italy

answer set programming (ASP) is a successful declarative formalism for knowledge representation and reasoning. The evaluation of ASP programs is nowadays based on the conflict-driven clause learning (CDCL) backtracking search algorithm. Recent work suggested that the performance of CDCL-based implementations can be considerably improved on specific benchmarks by extending their solving capabilities with custom heuristics and propagators. However, embedding such algorithms into existing systems requires expert knowledge of the internals of ASP implementations. The development of effective solver extensions can be made easier by providing suitable programming interfaces. In this paper, we present the interface for extending the CDCL-based ASP solver wasp. The interface is bothgeneral, that is, it can be used for providing either new branching heuristics or propagators, andexternal, that is, the implementation of new algorithms requires no internal modifications of wasp. Moreover, we review the applications of the interface witnessing it can be successfully used to extend wasp for solving effectively hard instances of both real-world and synthetic problems.

关键词： knowledge representation and reasoning answer set programming application programming interface propagators choice heuristics

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Structural constraints for dynamic operators in abstract argumentation

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ARGUMENT & COMPUTATION 2020年第1-2期11卷 151-190页

作者： Wallner, Johannes P. TU Wien Inst Log & Computat Vienna Austria

Many recent studies of dynamics in formal argumentation within AI focus on the well-known formalism of Dung's argumentation frameworks (AFs). Despite the usefulness of AFs in many areas of argumentation, their abstract notion of arguments creates a barrier for operators that modify a given AF, e.g., in the case that dependencies between arguments have been abstracted away that are important for subsequent modifications. In this paper we aim to support development of dynamic operators on formal models in abstract argumentation by providing constraints imposed on the modification of the structure that can be used to incorporate information that has been abstracted away. Towards a broad reach, we base our results on the general formalism of abstract dialectical frameworks (ADFs) in abstract argumentation. To show applicability, we present two cases studies that adapt an existing extension enforcement operator that modifies AFs: in the first case study, we show how to utilize constraints in order to obtain an enforcement operator on ADFs that is allowed to only add support relations between arguments, and in the second case study we show how an enforcement operator on AFs can be defined that respects dependencies between arguments. We show feasibility of our approach by studying the complexity of the proposed structural constraints and the operators arising from the case studies, and by an experimental evaluation of an answer set programming (ASP) implementation of the enforcement operator based on supports.

关键词： Abstract argumentation dynamics of argumentation argumentation frameworks abstract dialectical frameworks structured argumentation computational complexity constraints answer set programming

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Possible worlds explorer: Combining declarative programming with user-friendly Jupyter Notebooks

Possible worlds explorer: Combining declarative programming ...

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作者： Gupta, Sahil University of Illinois – Urbana-Champaign

学位级别：硕士

Datalog and answer set programming (ASP) are powerful languages for rule-based database querying and constraint solving, respectively. Similarly, Python is a popular and powerful procedural programming language with applications in many domains including data science. I have developed a problem solving framework called "Possible Worlds Exploration" which is based on combining the two programming paradigms to enable new exploration and problem solving capabilities for a wide audience of users. The primary component of this framework is the Possible Worlds Explorer (PWE), an open source Python-based toolkit that employs Jupyter Notebooks to make working with Datalog and ASP systems easier and more productive. PWE can parse output from different ASP reasoners (Clingo and DLV) and then run analytical queries over all answer sets or "possible worlds" (PWs), e.g., to calculate relative frequencies of atoms across PWs or to hierarchically cluster PWs based on user-defined complexity and similarity measures. PWE also has support for the three-valued well-founded semantics of Datalog programs (via DLV) and temporal models that use a special state argument. Using simple Python functions, generic as well as user-definable presentation and visualization formats can be easily created, e.g., to display all PWs (world views), the unique three-valued well founded model (partial views), and temporal models (timelines and time series). We have illustrated several examples, both theoretical and application-based, to showcase the abilities of PWE. We provide containerized versions of PWE that can be run in the cloud or locally. In this way the Possible Worlds Explorer makes Datalog and ASP more accessible for a wider audience.

关键词： Datalog answer set programming ASP Clingo DLV Stable Model Well-founded Python Tool Open source Possible Worlds Possible Worlds Explorer Jupyter Notebook Jupyter Notebook IPython Visualizations Framework PWE Framework PWE-NB-Extension Declarative programming Provenance Datalog Debugging Euler LeanEuler Taxonomy Alignment TAP CleanTax Education WODB

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Scheduling outpatient day service operations for rheumatology diseases

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FLEXIBLE SERVICES AND MANUFACTURING JOURNAL 2020年第1期32卷 102-128页

作者： Guido, Rosita Ielpa, Giuseppe Conforti, Domenico Univ Calabria Dept Mech Management Engn Via Pietro Bucci I-87036 Arcavacata Di Rende CS Italy Univ Calabria Dept Math Comp Sci Via Pietro Bucci Arcavacata Di Rende CS Italy Univ Calabria Dept Mech Energy & Management Engn Via Pietro Bucci I-87036 Arcavacata Di Rende CS Italy Univ Calabria Dept Math & Comp Sci Via Pietro Bucci Arcavacata Di Rende CS Italy

Appointment scheduling systems represent a method to manage patient waiting lists effectively. This work advances an innovative quantitative approach for the outpatient appointment scheduling problems, based on an optimization model, to manage outpatient Day Service operations. It focuses on outpatient appointment scheduling. We start from earlier works in the literature to design models with the objective to maximize the number of patients' appointments, to reduce patient's waiting time, and to increase patient's satisfaction. The proposed combinatorial problem is solved by answer set programming, which is a declarative logic formalism, widely used in Artificial Intelligence and recognized as a powerful tool for Knowledge Representation and Reasoning, to show the advantages of declarative programming for modelling and fast prototyping problem requirements. We apply the model to solve real-life scenarios of the Rheumatology domain. We compare the results on the real instance already solved in our earlier work and extend the computational experiments on some new generated and realistic instances. Since the computational times increase with the size of instances, we develop a three-phase solution approach based on patient's priority. The heuristic approach is hierarchical and enables to solve more instances than the one-run approach within the computational time limit.

关键词： Patient appointment scheduling Clinical pathways Patient-centred policies Ambulatory care Day service answer set programming Artificial intelligence

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A Model-Theoretic Approach to Belief Change in answer set programming

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ACM TRANSACTIONS ON COMPUTATIONAL LOGIC 2013年第2期14卷 14-14页

作者： Delgrande, James Schaub, Torsten Tompits, Hans Woltran, Stefan Simon Fraser Univ Burnaby BC V5A 1S6 Canada Univ Potsdam D-14482 Potsdam Germany Vienna Univ Technol A-1040 Vienna Austria

We address the problem of belief change in (nonmonotonic) logic programming under answer set semantics. Our formal techniques are analogous to those of distance-based belief revision in propositional logic. In particular, we build upon the model theory of logic programs furnished by SE interpretations, where an SE interpretation is a model of a logic program in the same way that a classical interpretation is a model of a propositional formula. Hence we extend techniques from the area of belief revision based on distance between models to belief change in logic programs. We first consider belief revision: for logic programs P and Q, the goal is to determine a program R that corresponds to the revision of P by Q, denoted P * Q. We investigate several operators, including (logic program) expansion and two revision operators based on the distance between the SE models of logic programs. It proves to be the case that expansion is an interesting operator in its own right, unlike in classical belief revision where it is relatively uninteresting. Expansion and revision are shown to satisfy a suite of interesting properties;in particular, our revision operators satisfy all or nearly all of the AGM postulates for revision. We next consider approaches for merging a set of logic programs, P-1,...,P-n. Again, our formal techniques are based on notions of relative distance between the SE models of the logic programs. Two approaches are examined. The first informally selects for each program P-i those models of P-i that vary the least from models of the other programs. The second approach informally selects those models of a program P-0 that are closest to the models of programs P-1,...,P-n. In this case, P-0 can be thought of as a set of database integrity constraints. We examine these operators with regards to how they satisfy relevant postulate sets. Last, we present encodings for computing the revision as well as the merging of logic programs within the same logic programming

关键词： Theory answer set programming belief revision belief merging program encodings strong equivalence

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AppMonitor: restricting information leakage to third-party applications

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SOCIAL NETWORK ANALYSIS AND MINING 2020年第1期10卷 1-20页

作者： Rathore, Nemi Chandra Tripathy, Somanath Indian Inst Technol Dept Comp Sci & Engn Patna Bihar India CUSB Gaya Bihar India

Nowadays, the popularity of online social networks (OSNs) has been increased tremendously. Meanwhile, a wide range of third-party applications (TPAs) facilitated by OSNs has made a significant contribution to their popularity. TPAs offer many attractive functionalities and services to the OSN users but pose serious privacy threats to the users. Therefore, it is essential to strictly regulate the divulgence of user data to TPAs. In this paper, we propose an access control framework calledAppMonitorto monitor and curb the user data to TPA. Further, we also introduce a relation-based access control policy model that uses predicate calculus to express data access policies. Analysis of the usability and correctness of the introduced policy model has been made, based on a logical model using answer set programming. A simplified prototype has been developed to show the feasibility of AppMonitor, and its effectiveness is shown through a user study.

关键词： Online social network Third-party application Privacy Access control answer set programming

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Towards a Logic programming Tool for Cancer Data Analysis

Towards a Logic Programming Tool for Cancer Data Analysis

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Fundamenta Informaticae

作者： Tarzariol, Alice Zanazzo, Eugenia Dovier, Agostino Policriti, Alberto Dipartimento di Scienze Matematiche Informatiche e Fisiche Università Degli Studi di Udine Italy

The main goal of this work is to propose a tool-chain capable of analyzing a data collection of temporally qualified (genetic) mutation profiles, i.e., a collection of DNA-sequences (genes) that present variations with respect to their 'healthy' versions. We implemented a system consisting of a front-end, a reasoning core, and a post-processor: the first transforms the input data retrieved from medical databases into a set of logical facts, while the last displays the computation results as graphs. Concerning the reasoning core, we employed the answer set programming paradigm, which is capable of deducing complex information from data. However, since the system is modular, this component can be replaced by any logic programming tool for different kinds of data analysis. Indeed, we tested the use of a probabilistic inductive logic programming core. © 2020 - IOS Press and the authors. All rights reserved.

关键词： Inductive logic programming (ILP) Computation theory Computer circuits Data handling DNA sequences Genetic programming Information analysis Medical computing answer set programming Complex information Data collection Front end Input datas Medical database Post processor Probabilistic inductive logic programming

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Paracoherent answer set computation

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ARTIFICIAL INTELLIGENCE 2021年 299卷 103519-103519页

作者： Amendola, Giovanni Dodaro, Carmine Faber, Wolfgang Ricca, Francesco Univ Calabria Dept Math & Comp Sci Calabria Italy Univ Genoa Dept Informat Bioengn Robot & Syst Engn Genoa Italy Alpen Adria Univ Klagenfurt Dept Appl Informat Klagenfurt Austria Univ Huddersfield Sch Comp & Engn Huddersfield W Yorkshire England

answer set programming (ASP) is a well-established paradigm for declarative programming and nonmonotonic reasoning. ASP allows for flexible modeling using rules. ASP rules induce a set of intended models called answer sets. Incoherence, the non-existence of answer sets, is therefore a feature of ASP, indicating that the rules admit no intended models. However, this feature can also be problematic in certain circumstances: errors that cause incoherence are notoriously difficult to debug, and query answering will not provide any meaningful answers for incoherent programs. Paracoherent semantics have been suggested as a remedy. They extend the classical notion of answer sets to draw meaningful conclusions also from incoherent programs. However, paracoherent semantics have essentially been inapplicable in practice, due to the lack of efficient algorithms and implementations. In this paper, this lack is addressed, and several different algorithms to compute semi-stable and semi-equilibrium models are proposed and implemented within an answer set solving framework. A key role in the framework is played by syntactic program transformations that allow for characterizing paracoherent semantics in terms of the answer sets of transformed programs. Apart from existing transformations from the literature, a novel transformation is also proposed, which provides an alternative characterization of paracoherent semantics in terms of (extended) externally supported models. Notably, the new transformation is more compact than the existing ones, and brings performance benefits. An extensive empirical performance comparison among the algorithms on benchmarks from ASP competitions and a real-world use case is given as well. It shows not only that the methods developed in this paper lead to practically effective systems, but also show a clear advantage of the methods that rely on (extended) externally supported models. (C) 2021 Elsevier B.V. All rights reserved.

关键词： answer set programming Paracoherent reasoning Semi-equilibrium models Semi-stable models

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