Statistical model learning problems are traditionally solved using either heuristic greedy optimization or stochastic simulation, such as Markov chain Monte Carlo or simulated annealing. Recently, there has been an in...
详细信息
Statistical model learning problems are traditionally solved using either heuristic greedy optimization or stochastic simulation, such as Markov chain Monte Carlo or simulated annealing. Recently, there has been an increasing interest in the use of combinatorial search methods, including those based on computational logic. Some of these methods are particularly attractive since they can also be successful in proving the global optimality of solutions, in contrast to stochastic algorithms that only guarantee optimality at the limit. Here we improve and generalize a recently introduced constraint-based method for learning undirected graphical models. The new method combines perfect elimination orderings with various strategies for solution pruning and offers a dramatic improvement both in terms of time and memory complexity. We also show that the method is capable of efficiently handling a more general class of models, called stratified/labeled graphical models, which have an astronomically larger model space.
The Artificial Intelligence (AI) has taken a leading role in many activities which used to be made "by hand";one of them is the musical composition. Such task now has another alternative implementation, thro...
详细信息
The Artificial Intelligence (AI) has taken a leading role in many activities which used to be made "by hand";one of them is the musical composition. Such task now has another alternative implementation, through the support of software that can compose different musical genres to the point where a computer can compose pieces with some autonomy. This paper proposes Armin, a system dedicated to the electronic trance music composition. Armins aim is to provide a trance music composition to serve as a template or a base audio file, ready to add more instruments in a mastering (remastering) production Additionally, it seeks to enable greater collaboration between a machine and a human, both seen as musical composers.
We introduce a new family of graphical models that consists of graphs with possibly directed, undirected and bidirected edges but without directed cycles. We show that these models are suitable for representing causal...
详细信息
We introduce a new family of graphical models that consists of graphs with possibly directed, undirected and bidirected edges but without directed cycles. We show that these models are suitable for representing causal models with additive error terms. We provide a set of sufficient graphical criteria for the identification of arbitrary causal effects when the new models contain directed and undirected edges but no bidirected edge. We also provide a necessary and sufficient graphical criterion for the identification of the causal effect of a single variable on the rest of the variables. Moreover, we develop an exact algorithm for learning the new models from observational and interventional data via answer set programming. Finally, we introduce gated models for causal effect identification, a new family of graphical models that exploits context specific independences to identify additional causal effects. (C) 2017 Elsevier Inc. All rights reserved.
Boolean games are a framework for reasoning about the rational behavior of agents whose goals are formalized using propositional formulas. Compared to normal form games, a well-studied and related game framework, Bool...
详细信息
Boolean games are a framework for reasoning about the rational behavior of agents whose goals are formalized using propositional formulas. Compared to normal form games, a well-studied and related game framework, Boolean games allow for an intuitive and more compact representation of the agents' goals. So far, Boolean games have been mainly studied in the literature from the Knowledge Representation perspective, and less attention has been paid on the algorithmic issues underlying the computation of solution concepts. Although some suggestions for solving specific classes of Boolean games have been made in the literature, there is currently no work available on the practical performance. In this paper, we propose the first technique to solve general Boolean games that does not require an exponential translation to normal-form games. Our method is based on disjunctive answer set programming and computes solutions (equilibria) of arbitrary Boolean games. It can be applied to a wide variety of solution concepts, and can naturally deal with extensions of Boolean games such as constraints and costs. We present detailed experimental results in which we compare the proposed method against a number of existing methods for solving specific classes of Boolean games, as well as adaptations of methods that were initially designed for normal-form games. We found that the heuristic methods that do not require all payoff matrix entries performed well for smaller Boolean games, while our ASP based technique is faster when the problem instances have a higher number of agents or action variables.
answer set programming (ASP) is a well-established declarative paradigm. One of the successes of ASP is the availability of efficient systems. State-of-the-art systems are based on the ground+solve approach. In some a...
详细信息
answer set programming (ASP) is a well-established declarative paradigm. One of the successes of ASP is the availability of efficient systems. State-of-the-art systems are based on the ground+solve approach. In some applications, this approach is infeasible because the grounding of one or a few constraints is expensive. In this paper, we systematically compare alternative strategies to avoid the instantiation of problematic constraints, which are based on custom extensions of the solver. Results on real and synthetic benchmarks highlight some strengths and weaknesses of the different strategies.
In this article, we present an encoding of the (recently proposed) denotational semantics for answer set programming (ASP) and its monotonic basis into the input language of the theorem prover PVS. Using some librarie...
详细信息
In this article, we present an encoding of the (recently proposed) denotational semantics for answer set programming (ASP) and its monotonic basis into the input language of the theorem prover PVS. Using some libraries and features from PVS, we have obtained semi-automated proofs for several fundamental properties of ASP. In this way, to the best of our knowledge, we provide the first known application of formal verification to ASP.
In this note, we consider the problem of introducing variables in temporal logic programs under the formalism of Temporal Equilibrium Logic, an extension of answer set programming for dealing with linear-time modal op...
详细信息
In this note, we consider the problem of introducing variables in temporal logic programs under the formalism of Temporal Equilibrium Logic, an extension of answer set programming for dealing with linear-time modal operators. To this aim, we provide a definition of a first-order version of Temporal Equilibrium Logic that shares the syntax of first-order Linear-time Temporal Logic but has different semantics, selecting some Linear-time Temporal Logic models we call temporal stable models. Then, we consider a subclass of theories (called splittable temporal logic programs) that are close to usual logic programs but allowing a restricted use of temporal operators. In this setting, we provide a syntactic definition of safe variables that suffices to show the property of domain independence - that is, addition of arbitrary elements in the universe does not vary the set of temporal stable models. Finally, we present a method for computing the derivable facts by constructing a non-temporal logic program with variables that is fed to a standard answer set programming grounder. The information provided by the grounder is then used to generate a subset of ground temporal rules which is equivalent to (and generally smaller than) the full program instantiation.
In this paper, we propose an extension of logic programming where each default literal derived from the well-founded model is associated to a justification represented as an algebraic expression. This expression conta...
详细信息
In this paper, we propose an extension of logic programming where each default literal derived from the well-founded model is associated to a justification represented as an algebraic expression. This expression contains both causal explanations (in the form of proof graphs built with rule labels) and terms under the scope of negation that stand for conditions that enable or disable the application of causal rules. Using some examples, we discuss how these new conditions, we respectively call enablers and inhibitors, are intimately related to default negation and have an essentially different nature from regular cause-effect relations. The most important result is a formal comparison to the recent algebraic approaches for justifications in logic programming: Why-not Provenance and Causal Graphs. We show that the current approach extends both Why-not Provenance and Causal Graphs justifications under the well-founded semantics and, as a byproduct, we also establish a formal relation between these two approaches.
In this paper, we define a class of nested logic programs, called Nested Logic Programs with Ordered Disjunction (LPODs(+)), which makes it possible to specify conditional (qualitative) preferences by means of nested ...
详细信息
In this paper, we define a class of nested logic programs, called Nested Logic Programs with Ordered Disjunction (LPODs(+)), which makes it possible to specify conditional (qualitative) preferences by means of nested preference statements. To this end, we augment the syntax of Logic Programs with Ordered Disjunction (LPODs) to capture more general expressions. We define the LPODs(+) semantics in a simple way and we extend most of the results of LPODs showing how our approach generalizes the LPODs framework in a proper way. We also show how the LPODs(+) semantics can be computed in terms of a translation procedure that maps a nested ordered disjunction program (OD+-program) into a disjunctive logic program.
This paper makes use of high-level action languages to investigate aspects of causality that are central to ethical reasoning. We identify properties that causal relations assume and that determine how, as well as to ...
详细信息
This paper makes use of high-level action languages to investigate aspects of causality that are central to ethical reasoning. We identify properties that causal relations assume and that determine how, as well as to what extent, we may ascribe ethical responsibility on their basis. The paper is structured in three parts. First, we present an extension of the Event Calculus that enables the agent to generate plans of actions, with the particularity that they integrate both actions and omissions. Second, we present an account of event-based causality that is grounded in the architecture of event preconditions and effects, and that distinguishes four types of causal relations contingent on the nature of the entities that compose them. Namely, it discriminates actions and omissions from automatic events, and produced outcomes from avoided ones. Third, we examine notions of scenario-based causality whose role it is to scrutinise and buttress the causal relations previously identified. Inquiring into the other possible versions of modelled scenarios, we account for simple counter-factual validity ("Had I not acted so, would this outcome still be true?"), criticality ("Could anything else have led to this outcome?"), extrinsic necessity ("Had I not produced it, was this outcome even avoidable?"), and elicited necessity ("Have I made this outcome unavoidable?"). The model is implemented in answer set programming.
暂无评论