Scielo RSS <![CDATA[Computación y Sistemas]]> vol. 21 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Editorial]]> <![CDATA[Action Models with Postconditions]]> Abstract: This work proposes a extension of dynamic epistemic logic to work with assignment. The difference between this work and others works, such as [7], is the use of actions models, from DEL, to make Boolean assignments to the propositions, instead of creating new mechanisms to make the assignments. We extend the definition of action model by creating the postcondition property of each state of the model, making it possible to assign Boolean values to the propositions. <![CDATA[Branching Path Planning with Modal Logics]]> Abstract: Path planning concerns about finding a route for an agent, such that this agent move along the route from an initial to a final goal. Some additional constraints may also have to be satisfied for the agent, such as avoiding obstacles or collisions. Path planning has been recently studied in the context of linear temporal logic with great success. Expressive constraint specifications involving temporal ordering can be succinctly expressed by logic formulas, whereas environments are abstracted as transition systems. The plan is obtained by counterexample generation in a model checking tool: finding a path, if any, such that a given formula (constraints) satisfies a given model (agent environment). Due to the expressive power of linear temporal logic, only linear planning has mostly been considered so far, that is, plans corresponding to tasks to be performed in a linear successive order. In this work, we study branching shaped (tree) plans in the context of the µ-calculus, an expressive modal logic which subsumes many program logics such as LTL, PDL and CTL. Branching plans can be succinctly expressed by logic formulas so that a team of mobile devices can concurrently satisfy the plan. In the current work, we provide a plan generator based on a model checking algorithm for the µ-calculus. We show the algorithm is sound and complete, that is, for any environment, there a satisfying plan for a given set of constraints, if and only if, the plan generator succeeds. <![CDATA[Implementing ∆<em><sub>ps</sub></em> (<em>PS-Merge</em>) Belief Merging Operator for Belief Revision]]> Abstract: Belief merging aims at combining information from multiple sources while belief revision studies strategies for retracting information in order to maintain consistency when the addition of new evidence to a belief base makes it inconsistent. An ordering of the sentences in the belief base is used to determine priorities among sentences so that those with lower priority can be identified and retracted. This ordering can be difficult to generate and maintain. To address this difficulty, in this paper we show how to generate automatically an ordering of the belief base sentences through the implementation of a belief merging operator. We extend the ∆ps (PS-Merge) belief merging operator in order to consider constraints, then we use this extension, called ∆ p s μ (∆ps under constraints), as a strategy for belief revision. We treat new evidence as a constraint and apply the extended merging operator to obtain the revised belief base. We propose several properties of this operator when compared to other two belief revision operators solving four examples described as real-life scenarios. Finally we show a software prototype based on this approach, called Belief Reviser, freely accessible online. <![CDATA[Model-based Algorithm for Belief Revisions between Normal. Conjunctive Forms]]> Resumen: La revisión de creencias es un área central en la representación de conocimiento y en el procesamiento de razonamiento automático. Consideraremos una base inicial de conocimiento K y una nueva información φ, ambas codificadas en forma normal conjuntiva (FC). Presentamos aquí, un algoritmo novedoso, determinista y correcto para la revisión de creencias de φ en K. Denotamos nuestro operador de revisión como: K′ = K ◦ φ. Proponemos un nuevo operador binario lógico Ind entre formas conjuntivas, y tal que Ind(φ, K) construye también una nueva forma conjuntiva. El operador Ind(φ, K) trabaja construyendo cláusulas independientes con las cláusulas de K, y las asignaciones falsificantes de la fórmula resultante cubren exactamente el espacio de asignaciones de F als(φ) − F als(K), lo que es esencial para realizar el proceso de revisión de creencias K′ = K ◦ φ, y donde K′ ⊨ φ. Además de que nuestra propuesta satisface los postulados KM. Presentamos también la demostración de que nuestro algoritmo de revisión de creencias es correcto, y su análisis de complejidad en tiempo.<hr/>Abstract: Belief revision is a central area in knowledge representation and processing of automated reasoning. We will consider a knowledge base (KB) K and a new information φ, both expressed in conjunctive form (CF). We present here, a novel, deterministic and correct algorithm for belief revision of φ in K. We denote our revision operator as: K′ = K ◦ φ. We introduce a new logical binary operator Ind between two conjunctive forms, such that Ind(φ, K) generates also a conjunctive form. The operator Ind(φ, K) works building independent clauses with the clauses of K, and whose falsifying assignments of the resulting formula cover exactly the space of assignments F als(φ) − F als(K), this is essential for performing the process of belief revision K′ = K ◦ φ, where K′ ⊨ φ. Furthermore, our proposal satisfies the KM postulates. We also present the correctness proof of our belief revision method, and the analysis of its time complexity. <![CDATA[Low-Exponential Algorithm for Counting the Number of Edge Cover on Simple Graphs]]> Abstract: A procedure for counting edge covers of simple graphs is presented. The procedure splits simple graphs into non-intersecting cycle graphs. This is a “low exponential” exact algorithm to count edge covers for simple graphs whose upper bound in the worst case is O(1.465575(m−n) × (m + n)), where m and n are the number of edges and nodes of the input graph, respectively. <![CDATA[0-1 Integer Programming for Computing Semi-Stable Semantics of Argumentation Frameworks]]> Abstract: Dung’s abstract argumentation has been an object of intense study not only due to its relationship with logical reasoning but also because of its uses within artificial intelligence. One research branch in abstract argumentation has focused on finding new methods for computing its different semantics. We present a novel method, to the best of our knowledge, for computing semi-stable semantics using 0-1 integer programming. This approach captures the notions of conflict freeness, acceptability, maximality with regard to set inclusion, etc., by 0-1 integer constraints. Additionally, this work also presents an empirical experiment to compare our novel approach with an answer set programming approach. Our results indicate that the new method performed well, and it has a great opportunity space for improving. <![CDATA[Numerical Investigation of the Droplet Behavior in Cascades Using a Finite Volume Method]]> Abstract: This paper describes an Eulerian/Lagrangian two-phase model for wet steam. Two-dimensional inviscid transonic cascade flow is simulated using a cell-vertex finite volume space discretization method on structured triangular mesh. A pseudo time scheme is used to march the solution to steady state. The model provides an approach for including the interaction between the liquid and gas phases for a pure fluid. The analysis consists in the application of the discrete phase model, for modeling the liquid particle flow, and the Eulerian conservation equations to the continuous phase. The investigation permits us to know the influence of parameters such as: particle diameter, flow angle and particle velocity on deposition of drops onto stator blade surfaces. These parameters are analyzed to different inlet flow angles and drop sizes in the turbine. Deposition rate was found to be strongly dependent on increasing inlet flow angle and drop size in the example computed. The purpose of this paper is to present the results of some calculations of deposition which are based on more recent theories or less simplified flow models than previously published work. <![CDATA[Trajectory Tracking of Complex Dynamical Network for Chaos Synchronization Using Recurrent Neural Network]]> Abstract: In this paper the problem of trajectory tracking is studied. Based on the Lyapunov theory, a control law that achieves the global asymptotic stability of the tracking error between a recurrent neural network and a complex dynamical network is obtained. To illustrate the analytic results we present a tracking simulation of a dynamical network with each node being just one Lorenz´s dynamical system and three identical Chen’s dynamical systems. <![CDATA[Performance Analysis of Simulated Annealing Cooling Schedules in the Context of Dense Image Matching]]> Abstract: Stochastic optimization is widely used in combinatorial computer vision problems, and many variant have been proposed. This contribution aims at analyzing and assessing several flavours of the simulated annealing algorithm. We particularly want to show the optimization performance, convergence speed, and quality of the solution with respect to the algorithm’s parameters and cooling schedules. We also verify experimentally that the S.A. algorithm is a global method i.e. it is able to lock a strong minimum regardless of the initialization. Performance evaluation is conducted in the context of stereo matching. <![CDATA[Model for Automatic Generation of Search-based Early Tests]]> Resumen: En el presente trabajo se presenta una propuesta para la generación de pruebas tempranas de software. La propuesta incluye las actividades para la ejecución de pruebas en un entorno productivo, así como el modelo de optimización que reduce la cantidad de casos de prueba funcionales considerando criterios de cobertura de escenario y utilizando algoritmos de búsqueda heurística. Adicionalmente el modelo contiene un conjunto de herramientas basadas en búsqueda que dan soporte a la generación de casos de pruebas funcionales.<hr/>Abstract: This article presents a proposal for the generation of software early tests. It includes: activities for test execution in a production environment, as well as the optimization model that reduces the number of functional test cases considering scenario covering criteria and using heuristic search algorithms. In addition, the model contains a collection of search-based tools that support the generation of functional test cases. <![CDATA[Segmentation Algorithm Applied to Seismic Images for Obtaining Potentially Hidden Geobodies]]> Resumen: La segmentación de imágenes es el proceso de extraer información con base en criterios de semejanza. En este artículo se propone un algoritmo de segmentación aplicado en imágenes a color con información sísmica en el espacio CIELAB. Dicho algoritmo, el IMP-2DMA, parte de un conjunto de valores iniciales proporcionados por el usuario, que forman parte de patrones en la imagen con ciertas características. Se realiza la asociación de píxeles con base en variables de control de expansión vertical y guías de dirección. Con los píxeles seleccionados se forma un conjunto de máscaras binarias 2D que serán parte de un volumen. Mediante una proyección tridimensional, las máscaras resultantes son visualizadas con efectos de luz y sombra, permitiendo apreciar geocuerpos complejos no visibles a primera vista. Los resultados muestran que con el IMP-2DMA se consigue extraer diversos patrones de manera similar a los obtenidos manualmente y con mayor precisión que con otros algoritmos de segmentación. Para evaluar el desempeño del IMP-2DMA se utilizó la prueba de suma de rangos de Wilcoxon. Las máscaras 2D fueron comparadas contra la solución ideal y la segmentación obtenida por un algoritmo de segmentación basado en umbral.<hr/>Abstract: Image segmentation is the process of extracting information based on similarity criteria. In this paper we propose a segmentation algorithm applied in color images with seismic information in the CIELAB space. This algorithm, the IMP-2DMA, takes a set of initial values provided by the user, which are part of patterns in the image with certain characteristics. The association of pixels based on vertical expansion control variables and direction guides is performed. With the selected pixels, a set of 2D binary masks will be formed that will be part of a volume. By means of a three-dimensional projection, the resulting masks are visualized with effects of light and shadow, allowing to appreciate complex geobodies not visible at first sight. The results show that with the IMP-2DMA it is possible to extract different patterns in a similar way to those obtained manually and more accurately than with other segmentation algorithms. The Wilcoxon rank sum test was used to evaluate the performance of the IMP-2DMA. The 2D masks were compared against the ideal solution and the segmentation obtained by a threshold-based segmentation algorithm. <![CDATA[Customer Relationship Management Systemic Model in Hotelier Sector: Are the Hotel Companies Gaining Benefits with Practices Oriented to the Relationship with the Clients?]]> Abstract: As a possibly potent business strategy that can give significant economic benefits for hotelier sectors and other companies, the topic of customer relationship management has tempted the organizations throughout the 1990s to date. One of the big problems is that many hotels have not seen the results they expected with their practice. On the other hand, it is now spoken that has been changed from a transactional marketing to a relational marketing, criticized for being difficult to implement in practice. Based on information collected from small and medium-sized hotel companies of three stars, classification based on the new hotel classification. The research findings show that the actual results being measured and achieved in hotelier sector are that the use of this type of strategy can allow hoteliers or companies to tailor special guest programs, services and promotions based on hotel guest preferences. The hotel can use the data collected in a program to identify the needs of customers across hotel chains to be able to use marketing that can be targeted at specific groups of people. It also gives hoteliers the opportunity to evaluate frequent guest programs, personalize their services and perform trend analysis. A program based in marketing relational is typically run by hotels and companies to collect guest information and transaction data for use and examining to allow hoteliers to see target groups that should be marketed too. Based on these transactions hotels can create and manage guest loyalty programs and reward schemes. This research approach is to appraise the impact of customer relationship management on customer profitability as mediated by customer loyalty and customer retention within the hotelier sector of Mexico, and specifically for those hoteliers classified like of three stars. A sample of 100 hotels three stars was interviewed as respondents in this study. The objective of the study was to find the impact relationship between effective customer relationship implementation, customer loyalty, and customer retention and customer profitability. The findings of the study add value to hotels three stars in Mexico, and provide some invaluable statistical results essential for hotel managers and owners to successfully enhance customer loyalty, customer retention and customer profitability. This study’s findings add to the body of knowledge and enable the managers of this sector to implement customer relationship management in the best shape possible, to match it with Mexican market-needs thereby creating more loyal customers. <![CDATA[Automatic Classification of Traced Neurons Using Morphological Features]]> Abstract: The great advances in the field of neuron tracing have made possible a high availability of free-access data in the Internet, which motivates the realization of automatic classifications. The increase of neuronal reconstruction databases makes the manual classification of neurons a time-consuming and tedious task for the analysts. Classification by human experts is also prone to inter- and intra-analyst variability due to the process’ inherent subjectivity. In this context, the need arises to find new descriptors having discriminative properties which allow separating the various neuron classes, and this constitutes currently an open problem. Such descriptors would contribute to improve the results of automatic classification. In this study the attention is focused on the use of new morphological features in supervised classification of traced neurons. Furthermore, we present a comparative analysis of different supervised learning algorithms oriented to the classification of reconstructed neurons. The results were validated using non-parametric statistical tests and they show the usefulness of the proposed solution. <![CDATA[Semantic-based Reconstruction of User’s Interests in Distributed Systems]]> Abstract: Generally, the user requires customized data reflecting his current needs represented in terms of interests that are stored in his profile. Therefore, taking into account user’s profile is significant to improve the returned results. Day by day, the user becomes more and more active in social networks and uses different distributed systems. In this context, the problem is that the access to user’s interests becomes more and more difficult mainly after updating and/or enriching the user’s profile. This may produce cognitive overload problem, which is time consuming in terms of browsing the user’s profile. This problem can be solved by reorganizing user’s interests. Most of the proposed reorganization methods use machine learning algorithms and different similarity measures. As the user’s interests are characterized by their popularity and freshness, other approaches combine these characteristics into the notion of temperature in order to keep in the profile uniquely the corresponding interests for a period of time. In this paper, we propose an approach to reconstruct the user’s profile by taking into account the semantic relationships between interests and by respectively merging the temperature and the k-means learning algorithm.