1,720,996 research outputs found
Conditional independence structure and its closure: inferential rules and algorithms
No full textIn this paper we deal with conditional independence models closed with respect to graphoid properties. Such models come from different uncertainty measures, in particular in a probabilistic coherent setting.
We study some inferential rules and describe methods and algorithms to compute
efficiently the closure of a set of conditional independence statements
An Evolutionary Algorithm for Adaptive Online Services in Dynamic Environment
No full textAn evolutionary adaptive algorithm for solving a class of online service provider problems in a dynamical web environment is introduced. In the online service provider scenario, a system continuously generates digital products and service instances by assembling components (e.g. headlines of online newspapers, search engine query results, advertising lists) to fulfill the requirements of a market of anonymous customers. The evaluation of a service instance can only be known by the feedback obtained after delivering it to the customer over the internet or through telephone networks. In dynamic domains available components and customer/agents preferences are changing over the time. The proposed algorithm employs typical genetic operators in order to optimize the service delivered and to adapt it to the environment feedback and evolution. Differently from classical genetic algorithms the goal of such systems is to maximize the average fitness instead of determining the single best optimal service/product. Experimental results for different classes of services, online newspapers and search engines, confirm the adaptive behavior of the proposed technique
A planning model for concurrent Asyncronus Automata
No full textIn this work a new approach based on planning paradigm is
proposed in order to describe the interactions of concurrent
asynchronous automata.
The behaviour of a set of nondeterministic asynchronous
automata which interact via common variables in a conflictfree environment is modelled through an appropriate
planning domain such that the set of valid plans in the
domain represents the set of possible behaviours of the
concurrent automata system. The consequence of the
method is that verifying and checking properties of the
automata system can be seen as solving appropriate
planning problems with additional constraints on solution
plans, such as temporally extended goals.
The proposed model allows a straightforward description of
automata in a portable and planner independent way, thus
recent advancements in plan synthesis algorithms can be
applied and exploited as well.
The validity of the approach has been experimentally
verified on recent planners in order to check properties of
classical examples of protocols in an automata community
such as deadlock and states reachability.
The approach represents in some sense the counterpart of
recent proposals based on planning via model checking.
The presented technique for modelling concurrent automata
by planning allows to extend the applicability of planners
not only to model checking but also to problems of
behaviours coordination, and plan synthesis with a plurality
of actor
A discrete differential evolution algorithm for multi-objective permutation flowshop scheduling
No full textThe more practical and interesting versions of the permutation flowshop scheduling problem (PFSP) have a variety of objective criteria to be optimized simultaneously. Multi-objective PFSP is also a relevant combinatorial multiobjective optimization problem. In this paper we propose a multi-objective evolutionary algorithm for PFSP by extending the previously proposed discrete differential evolution (DE) scheme for single-objective PFSP. This is the first application of the algebraic-based discrete DE to multi-objective problems. The algorithm is extended by adopting a variety of crossover and multi-objective selection operators. Among these, the multi-objective a-selection is a novelty of this work and can be decoupled from DE and used also in other evolutionary algorithms. The other crossover and selection operators have been taken from the existing literature and, where required, have been adapted to the problem at hand. An experimental evaluation has been conducted on all the three bi-objective PFSPs among the makespan, total flowtime and total tardiness criteria. The results show that the proposed approach is competitive with respect to the state-of-the-art algorithms
Algorithms for the closure of graphoid structures
No full textIn this paper we consider some conditional independence models associated to different uncertainty measures. In particular, we focus on the independence models closed with respect to graphoid properties and we describe methods and algorithms to compute efficiently the closure of a set of conditional independence relations
Solving permutation flowshop scheduling problems with a discrete differential evolution algorithm
No full textIn this paper a new discrete Differential Evolution algorithm for the Permutation Flowshop Scheduling Problem with the total flowtime and makespan criteria is proposed. The core of the algorithm is the distance-based differential mutation operator defined by means of a new randomized bubble sort algorithm. This mutation scheme allows the Differential Evolution to directly navigate the permutations search space. Experiments were held on a well known benchmarks suite and they show that the proposal reaches very good performances compared to other state-of-the-art algorithms. The results are particularly satisfactory on the total flowtime criterion where also new upper bounds that improve on the state-of-the-art have been found
Algorithms for possibility assessments: Coherence and extension
No full textIn this paper we study the computational aspects of coherence and extension of partial possibility assessments, both in an unconditional and a conditional setting, providing complexity results and algorithms for each problem. In particular, we propose an algorithm to check the coherence of a partial unconditional assessment which is based on propositional satisfiability. For the conditional case, we firstly prove a new characterization of coherent conditional assessments that allows us to define an algorithm
again based on propositional satisfiability. The extension problem, in both settings, is solved by means of a search algorithm which relies on the corresponding coherence procedure
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