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Rewriting recursive aggregates in answer set programming: back to monotonicity

THEORY AND PRACTICE OF LOGIC programming 2015年第4-5期15卷 559-573页

作者： Alviano, Mario Faber, Wolfgang Gebser, Martin Univ Calabria I-87030 Commenda Di Rende Italy Univ Huddersfield Huddersfield HD1 3DH W Yorkshire England Aalto Univ HIIT Espoo Finland

Aggregation functions are widely used in answer set programming for representing and reasoning on knowledge involving sets of objects collectively. Current implementations simplify the structure of programs in order to optimize the overall performance. In particular, aggregates are rewritten into simpler forms known as monotone aggregates. Since the evaluation of normal programs with monotone aggregates is in general on a lower complexity level than the evaluation of normal programs with arbitrary aggregates, any faithful translation function must introduce disjunction in rule heads in some cases. However, no function of this kind is known. The paper closes this gap by introducing a polynomial, faithful, and modular translation for rewriting common aggregation functions into the simpler form accepted by current solvers. A prototype system allows for experimenting with arbitrary recursive aggregates, which are also supported in the recent version 4.5 of the grounder GRINGO, using the methods presented in this paper.

关键词： answer set programming polynomial faithful and modular translation aggregation functions

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Decomposition approaches for scheduling chronic outpatients' clinical pathways in answer set programming

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JOURNAL OF LOGIC AND COMPUTATION 2023年第8期33卷 1851-1871页

作者： Cappanera, Paola Gavanelli, Marco Nonato, Maddalena Roma, Marco Univ Firenze DINFO Via S Marta 3 I-50139 Florence Italy Univ Ferrara DE Via Saragat 1 I-44122 Ferrara Italy

Chronic patients suffering from non-communicable diseases are often enrolled into a diagnostic and therapeutic care program featuring a personalized care plan. Healthcare is mostly provided at the patient's home, but those examinations and treatments that must be delivered at the hospital have to be explicitly booked. Booking is not trivial due to, on the one hand, the several time constraints that become particularly tight in the case of comorbidity, on the other hand, the limited availability of both staff and equipment at the hospital care units. This suggests that the scheduling of the clinical pathways for enrolled outpatients should be managed in a centralized manner, taking advantage of the fact that demand for services is known well in advance. The aim is to serve as many requests as possible (unattended requests are supplied by contracted private health facilities) in a timely manner, taking patients priority into account. Booking involves setting a date and a time for each selected health service, which is rather complex. In this work, we provide a declarative approach by encoding the problem in answer set programming (ASP). In order to improve the scalability of the ASP approach, we present and compare two heuristic approaches, respectively based on service demand and time decomposition. All approaches are tested on instances of increasing size to assess scalability with respect to time horizon and number of requests.

关键词： Clinical pathways outpatient appointment scheduling answer set programming decomposition approaches

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Updates in answer set programming: An approach based on basic structural properties

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THEORY AND PRACTICE OF LOGIC programming 2007年第4期7卷 451-479页

作者： Osorio, Maurico Cuevas, Victor Univ Americas Puebla Cholula 72820 Mexico

We have studied the update operator circle plus(1) defined for update sequences by Eiter et al. without tautologies and we have observed that it satisfies an interesting property(1). This property, which we call Weak Independence of Syntax (WIS), is similar to one of the postulates proposed by Alchourron, Gardenfors, and Makinson (AGM);only that in this case it applies to nonmonotonic logic. In addition, we consider other five additional basic properties about update programs and we show that circle plus(1) satisfies them. This work continues the analysis of the AGM postulates with respect to the circle plus(1) operator under a refined view that considers N-2 as a monotonic logic which allows us to expand our understanding of answer sets. Moreover, N-2 helped us to derive an alternative definition of circle plus(1) avoiding the use of unnecessary extra atoms.

关键词： answer set programming N-2 logic update programs strong negation AGM postulates

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Modeling adaptive access control policies using answer set programming

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JOURNAL OF INFORMATION SECURITY AND APPLICATIONS 2019年第Feb.期44卷 49-63页

作者： Sartoli, Sara Namin, Akbar Siami Univ North Georgia Dept Comp Sci & Informat Syst Dahlonega GA USA Texas Tech Univ Comp Sci Dept Lubbock TX 79409 USA

Many of the existing management platforms such as pervasive computing systems implement policies that depend on dynamic operational environment changes. Existing formal approaches for automatically enforcing access control policies are primarily expressed in conventional logic programming, also known as monotonic logics, e.g., First Order Logic (FOL). The major issue with monotonic logics is that they are not devised to invalidate initial believes in the light of further observations. This limitation makes these traditional logical approaches less suitable for modeling and analyzing context-aware access control policies, where exceptional policies are introduced incrementally and adaptively during runtime. The inability to invalidate initial policies when an exception needs to be enforced might result in inconsistencies and violations that need to be resolved manually by human entities. To address the problems with conventional logical approaches and more importantly prevent such inconsistencies, this paper presents a non-monotonic logic-based reasoning scheme for modeling and analyzing adaptive access control policies. In the proposed formalism, unavailable context data and incomplete access control policies can be explicitly expressed. To do so, the paper distinguishes three kinds of policies: default, context-dependent and exception policies. The proposed formalism is based on answer set programming (ASP), a non-monotonic logic programming language that allows elegant representation of unavailability of context data in adaptive systems. We devise non-monotonic policy inference rules such that, when exception policies are defined, they take precedence over default and context-dependent policies automatically. The results of two case studies are reported to demonstrate the feasibility of the proposed policy representation scheme compared to the Organizational-Based Access Control (OrBAC) model. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Access control Inference mechanism answer set programming Policies Exception handling Conflict

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A Constructive semantic characterization of aggregates in answer set programming

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THEORY AND PRACTICE OF LOGIC programming 2007年第3期7卷 355-375页

作者： Son, Tran Cao Pontelli, Enrico New Mexico State Univ Dept Comp Sci Albuquerque NM 87131 USA

This technical note describes a monotone and continuous fixpoint operator to compute the answer sets of programs with aggregates. The fixpoint operator relies on the notion of aggregate solution. Under certain conditions, this operator behaves identically to the three-valued immediate consequence operator Phi(aggr)(P) for aggregate programs, independently proposed in Pelov (2004) and Pelov et al. (2004). This operator allows us to closely tie the computational complexity of the answer set checking and answer sets existence problems to the cost of checking a solution of the aggregates in the program. Finally, we relate the semantics described by the operator to other proposals for logic programming with aggregates.

关键词： aggregates answer set programming semantics

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Generating Global and Local Explanations for Tree-Ensemble Learning Methods by answer set programming

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THEORY AND PRACTICE OF LOGIC programming 2024年第5期24卷 973-1010页

作者： Takemura, Akihiro Inoue, Katsumi SOKENDAI Grad Univ Adv Studies Chiyoda Ku Tokyo Japan Natl Inst Informat Chiyoda Ku Tokyo Japan

We propose a method for generating rule sets as global and local explanations for tree-ensemble learning methods using answer set programming (ASP). To this end, we adopt a decompositional approach where the split structures of the base decision trees are exploited in the construction of rules, which in turn are assessed using pattern mining methods encoded in ASP to extract explanatory rules. For global explanations, candidate rules are chosen from the entire trained tree-ensemble models, whereas for local explanations, candidate rules are selected by only considering rules that are relevant to the particular predicted instance. We show how user-defined constraints and preferences can be represented declaratively in ASP to allow for transparent and flexible rule set generation, and how rules can be used as explanations to help the user better understand the models. Experimental evaluation with real-world datasets and popular tree-ensemble algorithms demonstrates that our approach is applicable to a wide range of classification tasks.

关键词： answer set programming machine learning explainability decision trees rule sets pattern mining

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Semantics and complexity of recursive aggregates in answer set programming

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ARTIFICIAL INTELLIGENCE 2011年第1期175卷 278-298页

作者： Faber, Wolfgang Pfeifer, Gerald Leone, Nicola Univ Calabria Dept Math I-87030 Arcavacata Di Rende CS Italy

The addition of aggregates has been one of the most relevant enhancements to the language of answer set programming (ASP). They strengthen the modelling power of ASP in terms of natural and concise problem representations. Previous semantic definitions typically agree in the case of non-recursive aggregates, but the picture is less clear for aggregates involved in recursion. Some proposals explicitly avoid recursive aggregates, most others differ, and many of them do not satisfy desirable criteria, such as minimality or coincidence with answer sets in the aggregate-free case. In this paper we define a semantics for programs with arbitrary aggregates (including monotone, antimonotone, and nonmonotone aggregates) in the full ASP language allowing also for disjunction in the head (disjunctive logic programming - DLP). This semantics is a genuine generalization of the answer set semantics for DLP, it is defined by a natural variant of the Gelfond-Lifschitz transformation, and treats aggregate and non-aggregate literals in a uniform way. This novel transformation is interesting per se also in the aggregate-free case, since it is simpler than the original transformation and does not need to differentiate between positive and negative literals. We prove that our semantics guarantees the minimality (and therefore the incomparability) of answer sets, and we demonstrate that it coincides with the standard answer set semantics on aggregate-free programs. Moreover, we carry out an in-depth study of the computational complexity of the language. The analysis pays particular attention to the impact of syntactical restrictions on programs in the form of limited use of aggregates, disjunction, and negation. While the addition of aggregates does not affect the complexity of the full DLP language, it turns out that their presence does increase the complexity of normal (i.e., non-disjunctive) ASP programs up to the second level of the polynomial hierarchy. However, we show that there a

关键词： Nonmonotonic reasoning answer set programming Aggregates Computational complexity

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The third open answer set programming competition

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THEORY AND PRACTICE OF LOGIC programming 2014年第1期14卷 117-135页

作者： Calimeri, Francesco Ianni, Giovambattista Ricca, Francesco Univ Calabria Dipartimento Matemat I-87030 Commenda Di Rende Italy

answer set programming (ASP) is a well-established paradigm of declarative programming in close relationship with other declarative formalisms such as SAT Modulo Theories, Constraint Handling Rules, FO(.), PDDL and many others. Since its first informal editions, ASP systems have been compared in the now well-established ASP Competition. The Third (Open) ASP Competition, as the sequel to the ASP Competitions Series held at the University of Potsdam in Germany (2006-2007) and at the University of Leuven in Belgium in 2009, took place at the University of Calabria (Italy) in the first half of 2011. Participants competed on a pre-selected collection of benchmark problems, taken from a variety of domains as well as real world applications. The Competition ran on two tracks: the Model and Solve (M&S) Track, based on an open problem encoding, and open language, and open to any kind of system based on a declarative specification paradigm;and the System Track, run on the basis of fixed, public problem encodings, written in a standard ASP language. This paper discusses the format of the competition and the rationale behind it, then reports the results for both tracks. Comparison with the second ASP competition and state-of-the-art solutions for some of the benchmark domains is eventually discussed.

关键词： answer set programming logic programming declarative languages artificial intelligence competitions

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Reducing fuzzy answer set programming to model finding in fuzzy logics

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THEORY AND PRACTICE OF LOGIC programming 2012年第06期12卷 811-842页

作者： Janssen, Jeroen Vermeir, Dirk Schockaert, Steven De Cock, Martine Vrije Univ Brussel Dept Comp Sci B-1050 Brussels Belgium Univ Ghent Dept Appl Math & Comp Sci B-9000 Ghent Belgium Univ Washington Inst Technol Tacoma WA 98402 USA

In recent years, answer set programming (ASP) has been extended to deal with multivalued predicates. The resulting formalisms allow for the modeling of continuous problems as elegantly as ASP allows for the modeling of discrete problems, by combining the stable model semantics underlying ASP with fuzzy logics. However, contrary to the case of classical ASP where many efficient solvers have been constructed, to date there is no efficient fuzzy ASP solver. A well-known technique for classical ASP consists of translating an ASP program P to a propositional theory whose models exactly correspond to the answer sets of P. In this paper, we show how this idea can be extended to fuzzy ASP, paving the way to implement efficient fuzzy ASP solvers that can take advantage of existing fuzzy logic reasoners.

关键词： fuzzy logic answer set programming ASSAT

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Discriminate the response of Acute Myeloid Leukemia patients to treatment by using proteomics data and answer set programming

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BMC BIOINFORMATICS 2018年第2期19卷 15-26页

作者： Chebouba, Lokmane Miannay, Bertrand Boughaci, Dalila Guziolowski, Carito USTHB Elect Engn & Comp Sci Fac Dept Comp Sci LRIA Lab El Alia BP 32 Bab Ezzouar Algiers 16111 Algeria Ecole Cent Nantes LS2N UMR 6004 Nantes France

Background: During the last years, several approaches were applied on biomedical data to detect disease specific proteins and genes in order to better target drugs. It was shown that statistical and machine learning based methods use mainly clinical data and improve later their results by adding omics data. This work proposes a new method to discriminate the response of Acute Myeloid Leukemia (AML) patients to treatment. The proposed approach uses proteomics data and prior regulatory knowledge in the form of networks to predict cancer treatment outcomes by finding out the different Boolean networks specific to each type of response to drugs. To show its effectiveness we evaluate our method on a dataset from the DREAM 9 challenge. Results: The results are encouraging and demonstrate the benefit of our approach to distinguish patient groups with different response to treatment. In particular each treatment response group is characterized by a predictive model in the form of a signaling Boolean network. This model describes regulatory mechanisms which are specific to each response group. The proteins in this model were selected from the complete dataset by imposing optimization constraints that maximize the difference in the logical response of the Boolean network associated to each group of patients given the omic dataset. This mechanistic and predictive model also allow us to classify new patients data into the two different patient response groups. Conclusions: We propose a new method to detect the most relevant proteins for understanding different patient responses upon treatments in order to better target drugs using a Prior Knowledge Network and proteomics data. The results are interesting and show the effectiveness of our method.

关键词： AML answer set programming Boolean network Proteomics data

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