Departament de Ciències de la Computació
http://hdl.handle.net/2117/3971
Sat, 22 Apr 2017 14:03:23 GMT2017-04-22T14:03:23ZDynamic learning of cases from data streams
http://hdl.handle.net/2117/103610
Dynamic learning of cases from data streams
Orduña Cabrera, Fernando; Sànchez-Marrè, Miquel
This paper presents a dynamic adaptive framework for building a case library being able to cope with a data stream in the field of Case-Based Reasoning. The framework provides a three-layer architecture formed by a set of case libraries dynamically built. This Dynamic and Adaptive Case Library (DACL), can process in an incremental way a data stream, and can be used as a classification model or a regression model, depending on the predicted variable. In this paper, the work is focused on classification tasks. Each case library has a first layer formed by the dynamic clusters of cases, a second one formed by the meta-cases or prototypes of the cluster, and a third one formed by an incremental indexing structure. In our approach, some variant of k-d tres have been used, in addition to an exploration technique to get a more efficient retrieval time. This three-layer famework can be constructed in an incremental way. Several meta-case learning approaches are proposed, as well as some case learning strategies. The framework has been tested with several datasets. The experimental results show a very good performance in comparison with a batch learning scheme over the same data.
Fri, 21 Apr 2017 10:52:05 GMThttp://hdl.handle.net/2117/1036102017-04-21T10:52:05ZOrduña Cabrera, FernandoSànchez-Marrè, MiquelThis paper presents a dynamic adaptive framework for building a case library being able to cope with a data stream in the field of Case-Based Reasoning. The framework provides a three-layer architecture formed by a set of case libraries dynamically built. This Dynamic and Adaptive Case Library (DACL), can process in an incremental way a data stream, and can be used as a classification model or a regression model, depending on the predicted variable. In this paper, the work is focused on classification tasks. Each case library has a first layer formed by the dynamic clusters of cases, a second one formed by the meta-cases or prototypes of the cluster, and a third one formed by an incremental indexing structure. In our approach, some variant of k-d tres have been used, in addition to an exploration technique to get a more efficient retrieval time. This three-layer famework can be constructed in an incremental way. Several meta-case learning approaches are proposed, as well as some case learning strategies. The framework has been tested with several datasets. The experimental results show a very good performance in comparison with a batch learning scheme over the same data.Clustering of exchange rates and their dynamics under different dependence measures
http://hdl.handle.net/2117/103560
Clustering of exchange rates and their dynamics under different dependence measures
Renedo, Martí; Arratia Quesada, Argimiro Alejandro
This paper proposes an improvement to the method for clustering exchange rates given by D. J. Fenn et al, in Quantitative Finance, 12 (10) 2012, pp.1493-1520. To deal with the potentially non linear nature of currency time series dependence, we propose two alternative similarity metrics to use instead of the one used in the aforementioned paper based on Pearson correlation. Our proposed similarity metrics are based upon Kendall and distance correlations. We observe how each of the newly adapted clustering methods respond over several years of currency exchange data and find significant differences in the resulting clusters.
Thu, 20 Apr 2017 07:46:25 GMThttp://hdl.handle.net/2117/1035602017-04-20T07:46:25ZRenedo, MartíArratia Quesada, Argimiro AlejandroThis paper proposes an improvement to the method for clustering exchange rates given by D. J. Fenn et al, in Quantitative Finance, 12 (10) 2012, pp.1493-1520. To deal with the potentially non linear nature of currency time series dependence, we propose two alternative similarity metrics to use instead of the one used in the aforementioned paper based on Pearson correlation. Our proposed similarity metrics are based upon Kendall and distance correlations. We observe how each of the newly adapted clustering methods respond over several years of currency exchange data and find significant differences in the resulting clusters.Immunity and simplicity in relativizations of probabilistic complexity classes
http://hdl.handle.net/2117/103554
Immunity and simplicity in relativizations of probabilistic complexity classes
Balcázar Navarro, José Luis; Russo, David A.
The existence of immune and simple sets in relativizations of the probabilistic polynomial time bounded classes is studied. Some techniques previously used to show similar results for relativizations of P and NP are adapted to the probabilistic classes. Using these results, an exhaustive settling of all possible strong separations among these relativized classes is obtained.; On étudie les relativisations des classes de complexité probabiliste polynômiale. On adapte aux classes probabilistes des techniques déjà utilisées pour établir des résultats similaires pour les relativisations de P et NP. On obtient à partir de ces résultats une classification de toutes les propriétés de séparation forte pour ces classes relativisées.
Wed, 19 Apr 2017 14:00:20 GMThttp://hdl.handle.net/2117/1035542017-04-19T14:00:20ZBalcázar Navarro, José LuisRusso, David A.The existence of immune and simple sets in relativizations of the probabilistic polynomial time bounded classes is studied. Some techniques previously used to show similar results for relativizations of P and NP are adapted to the probabilistic classes. Using these results, an exhaustive settling of all possible strong separations among these relativized classes is obtained.
On étudie les relativisations des classes de complexité probabiliste polynômiale. On adapte aux classes probabilistes des techniques déjà utilisées pour établir des résultats similaires pour les relativisations de P et NP. On obtient à partir de ces résultats une classification de toutes les propriétés de séparation forte pour ces classes relativisées.Sparse sets, lowness, and highness
http://hdl.handle.net/2117/103245
Sparse sets, lowness, and highness
Balcázar Navarro, José Luis; Book, R; Schoening, U
We develop the notions of “generalized lowness” for sets in PH (the union of the polynomial-time hierarchy) and of “generalized highness” for arbitrary sets. Also, we develop the notions of “extended lowness” and “extended highness” for arbitrary sets. These notions extend the decomposition of NP into low sets and high sets developed by Schöning [15] and studied by Ko and Schöning [9].
We show that either every sparse set in PH is generalized high or no sparse set in PH is generalized high. Further, either every sparse set is extended high or no sparse set is extended high. In both situations, the former case corresponds to the polynomial-time hierarchy having only finitely many levels while the latter case corresponds to the polynomial-time hierarchy extending infinitely many levels.
Tue, 04 Apr 2017 07:57:03 GMThttp://hdl.handle.net/2117/1032452017-04-04T07:57:03ZBalcázar Navarro, José LuisBook, RSchoening, UWe develop the notions of “generalized lowness” for sets in PH (the union of the polynomial-time hierarchy) and of “generalized highness” for arbitrary sets. Also, we develop the notions of “extended lowness” and “extended highness” for arbitrary sets. These notions extend the decomposition of NP into low sets and high sets developed by Schöning [15] and studied by Ko and Schöning [9].
We show that either every sparse set in PH is generalized high or no sparse set in PH is generalized high. Further, either every sparse set is extended high or no sparse set is extended high. In both situations, the former case corresponds to the polynomial-time hierarchy having only finitely many levels while the latter case corresponds to the polynomial-time hierarchy extending infinitely many levels.The complexity of testing properties of simple games
http://hdl.handle.net/2117/103171
The complexity of testing properties of simple games
Freixas Bosch, Josep; Molinero Albareda, Xavier; Olsen, Martin; Serna Iglesias, María José
Simple games cover voting systems in which a single alternative, such as a bill or an amendment, is pitted against the status quo. A simple game or a yes-no voting system is a set of rules that specifies exactly which collections of ``yea'' votes yield passage of the issue at hand. A collection of ``yea'' voters forms a winning coalition.
We are interested on performing a complexity analysis of problems on such games depending on the game representation. We consider four natural explicit representations, winning, loosing, minimal winning, and maximal loosing. We first analyze the computational complexity of obtaining a particular representation of a simple game from a different one. We show that some cases this transformation can be done in polynomial time while the others require exponential time. The second question is classifying the complexity for testing whether a game is simple or weighted. We show that for the four types of representation both problem can be solved in polynomial time. Finally, we provide results on the complexity of testing whether a simple game or a weighted game is of a special type. In this way, we analyze strongness, properness, decisiveness and homogeneity, which are desirable properties to be fulfilled for a simple game.
Fri, 31 Mar 2017 15:48:07 GMThttp://hdl.handle.net/2117/1031712017-03-31T15:48:07ZFreixas Bosch, JosepMolinero Albareda, XavierOlsen, MartinSerna Iglesias, María JoséSimple games cover voting systems in which a single alternative, such as a bill or an amendment, is pitted against the status quo. A simple game or a yes-no voting system is a set of rules that specifies exactly which collections of ``yea'' votes yield passage of the issue at hand. A collection of ``yea'' voters forms a winning coalition.
We are interested on performing a complexity analysis of problems on such games depending on the game representation. We consider four natural explicit representations, winning, loosing, minimal winning, and maximal loosing. We first analyze the computational complexity of obtaining a particular representation of a simple game from a different one. We show that some cases this transformation can be done in polynomial time while the others require exponential time. The second question is classifying the complexity for testing whether a game is simple or weighted. We show that for the four types of representation both problem can be solved in polynomial time. Finally, we provide results on the complexity of testing whether a simple game or a weighted game is of a special type. In this way, we analyze strongness, properness, decisiveness and homogeneity, which are desirable properties to be fulfilled for a simple game.Improving IntSat by expressing disjunctions of bounds as linear constraints
http://hdl.handle.net/2117/103144
Improving IntSat by expressing disjunctions of bounds as linear constraints
Asín Acha, Roberto Javier; Aloysius Bezem, Marcus; Nieuwenhuis, Robert Lukas Mario
Conflict-Driven Clause Learning (CDCL) SAT solvers can automatically solve very large real-world problems. IntSat is a new technique extending CDCL to Integer Linear Programming (ILP). For some conflicts, IntSat generates no strong enough ILP constraint, and the backjump has to be done based on the conflicting set of bounds. The techniques given in this article precisely analyze how and when that set can be translated into the required new ILP constraint. Moreover, this can be done efficiently. This obviously strengthens learning and significantly improves the performance of IntSat (as confirmed by our experiments). We also briefly discuss extensions and other applications.
Fri, 31 Mar 2017 10:33:34 GMThttp://hdl.handle.net/2117/1031442017-03-31T10:33:34ZAsín Acha, Roberto JavierAloysius Bezem, MarcusNieuwenhuis, Robert Lukas MarioConflict-Driven Clause Learning (CDCL) SAT solvers can automatically solve very large real-world problems. IntSat is a new technique extending CDCL to Integer Linear Programming (ILP). For some conflicts, IntSat generates no strong enough ILP constraint, and the backjump has to be done based on the conflicting set of bounds. The techniques given in this article precisely analyze how and when that set can be translated into the required new ILP constraint. Moreover, this can be done efficiently. This obviously strengthens learning and significantly improves the performance of IntSat (as confirmed by our experiments). We also briefly discuss extensions and other applications.Computing alignments with constraint programming : the acyclic case
http://hdl.handle.net/2117/103063
Computing alignments with constraint programming : the acyclic case
Borrego, Diana; Gómez López, María Teresa; Carmona Vargas, Josep; Martínez Gasca, Rafael
Conformance checking confronts process models with real process executions to detect and measure deviations between modelled and observed behaviour. The core technique for conformance checking is the computation of an alignment. Current approaches for alignment computation rely on a shortest-path technique over the product of the state-space of a model and the observed trace, thus suffering from the well-known state explosion problem. This paper presents a fresh alternative for alignment computation of acyclic process models, that encodes the alignment problem as a Constraint Satisfaction Problem. Since modern solvers for this framework are capable of dealing with large instances, this contribution has a clear potential. Remarkably, our prototype implementation can handle instances that represent a real challenge for current techniques. Main advantages of using Constraint Programming paradigm lie in the possibility to adapt parameters such as the maximum search time, or the maximum misalignment allowed. Moreover, using search and propagation algorithms incorporated in Constraint Programming Solvers permits to find solutions for problems unsolvable with other techniques.
Thu, 30 Mar 2017 06:45:05 GMThttp://hdl.handle.net/2117/1030632017-03-30T06:45:05ZBorrego, DianaGómez López, María TeresaCarmona Vargas, JosepMartínez Gasca, RafaelConformance checking confronts process models with real process executions to detect and measure deviations between modelled and observed behaviour. The core technique for conformance checking is the computation of an alignment. Current approaches for alignment computation rely on a shortest-path technique over the product of the state-space of a model and the observed trace, thus suffering from the well-known state explosion problem. This paper presents a fresh alternative for alignment computation of acyclic process models, that encodes the alignment problem as a Constraint Satisfaction Problem. Since modern solvers for this framework are capable of dealing with large instances, this contribution has a clear potential. Remarkably, our prototype implementation can handle instances that represent a real challenge for current techniques. Main advantages of using Constraint Programming paradigm lie in the possibility to adapt parameters such as the maximum search time, or the maximum misalignment allowed. Moreover, using search and propagation algorithms incorporated in Constraint Programming Solvers permits to find solutions for problems unsolvable with other techniques.Can 3D gamified simulations be valid vocational training tools for persons with intellectual disability? A pilot based on a real-life situation
http://hdl.handle.net/2117/102971
Can 3D gamified simulations be valid vocational training tools for persons with intellectual disability? A pilot based on a real-life situation
von Barnekow, Ariel; Bonet Codina, Núria; Tost Pardell, Daniela
Objective: To investigate if 3D gamified simulations can be valid vocational training tools for persons with intellectual disability. Methods: A 3D gamified simulation composed by a set of training tasks for cleaning in hostelry was developed in collaboration with professionals of a real hostel and pedagogues of a special needs school. The learning objectives focus on the acquisition of vocabulary skills, work procedures, social abilities and risk prevention. Several accessibility features were developed to make the tasks easy to do from a technological point-of-view. A pilot experiment was conducted to test the pedagogical efficacy of this tool on intellectually disabled workers and students. Results: User scores in the gamified simulation follow a curve of increasing progression. When confronted with reality, they recognized the scenario and tried to reproduce what they had learned in the simulation. Finally, they were interested in the tool, they showed a strong feeling of immersion and engagement, and they reported having fun. Conclusions: On the basis of this experiment we believe that 3D gamified simulations can be efficient tools to train social and professional skills of persons with intellectual disabilities contributing thus to foster their social inclusion through work.
Tue, 28 Mar 2017 13:31:23 GMThttp://hdl.handle.net/2117/1029712017-03-28T13:31:23Zvon Barnekow, ArielBonet Codina, NúriaTost Pardell, DanielaObjective: To investigate if 3D gamified simulations can be valid vocational training tools for persons with intellectual disability. Methods: A 3D gamified simulation composed by a set of training tasks for cleaning in hostelry was developed in collaboration with professionals of a real hostel and pedagogues of a special needs school. The learning objectives focus on the acquisition of vocabulary skills, work procedures, social abilities and risk prevention. Several accessibility features were developed to make the tasks easy to do from a technological point-of-view. A pilot experiment was conducted to test the pedagogical efficacy of this tool on intellectually disabled workers and students. Results: User scores in the gamified simulation follow a curve of increasing progression. When confronted with reality, they recognized the scenario and tried to reproduce what they had learned in the simulation. Finally, they were interested in the tool, they showed a strong feeling of immersion and engagement, and they reported having fun. Conclusions: On the basis of this experiment we believe that 3D gamified simulations can be efficient tools to train social and professional skills of persons with intellectual disabilities contributing thus to foster their social inclusion through work.The HOM problem is EXPTIME-complete
http://hdl.handle.net/2117/102817
The HOM problem is EXPTIME-complete
Creus López, Carles; Gascon Caro, Adrian; Godoy Balil, Guillem; Ramos Garrido, Lander
We define a new class of tree automata with constraints and prove decidability of the emptiness problem for this class in exponential time. As a consequence, we obtain several EXPTIME-completeness results for problems on images of regular tree languages under tree homomorphisms, like set inclusion, regularity (HOM problem), and finiteness of set difference. Our result also has implications in term rewriting, since the set of reducible terms of a term rewrite system can be described as the image of a tree homomorphism. In particular, we prove that inclusion of sets of normal forms of term rewrite systems can be decided in exponential time. Analogous consequences arise in the context of XML typechecking, since types are defined by tree automata and some type transformations are homomorphic.
Thu, 23 Mar 2017 09:26:34 GMThttp://hdl.handle.net/2117/1028172017-03-23T09:26:34ZCreus López, CarlesGascon Caro, AdrianGodoy Balil, GuillemRamos Garrido, LanderWe define a new class of tree automata with constraints and prove decidability of the emptiness problem for this class in exponential time. As a consequence, we obtain several EXPTIME-completeness results for problems on images of regular tree languages under tree homomorphisms, like set inclusion, regularity (HOM problem), and finiteness of set difference. Our result also has implications in term rewriting, since the set of reducible terms of a term rewrite system can be described as the image of a tree homomorphism. In particular, we prove that inclusion of sets of normal forms of term rewrite systems can be decided in exponential time. Analogous consequences arise in the context of XML typechecking, since types are defined by tree automata and some type transformations are homomorphic.Acoustic sequences in non-human animals: a tutorial review and prospectus
http://hdl.handle.net/2117/102816
Acoustic sequences in non-human animals: a tutorial review and prospectus
Kershenbaum, Arik; Blumstein, Daniel T.; Roch, Marie A.; Ferrer Cancho, Ramon
Animal acoustic communication often takes the form of complex sequences, made up of multiple distinct acoustic units. Apart from the well-known example of birdsong, other animals such as insects, amphibians, and mammals (including bats, rodents, primates, and cetaceans) also generate complex acoustic sequences. Occasionally, such as with birdsong, the adaptive role of these sequences seems clear (e.g. mate attraction and territorial defence). More often however, researchers have only begun to characterise-let alone understand-the significance and meaning of acoustic sequences. Hypotheses abound, but there is little agreement as to how sequences should be defined and analysed. Our review aims to outline suitable methods for testing these hypotheses, and to describe the major limitations to our current and near-future knowledge on questions of acoustic sequences. This review and prospectus is the result of a collaborative effort between 43 scientists from the fields of animal behaviour, ecology and evolution, signal processing, machine learning, quantitative linguistics, and information theory, who gathered for a 2013 workshop entitled, 'Analysing vocal sequences in animals'. Our goal is to present not just a review of the state of the art, but to propose a methodological framework that summarises what we suggest are the best practices for research in this field, across taxa and across disciplines. We also provide a tutorial-style introduction to some of the most promising algorithmic approaches for analysing sequences. We divide our review into three sections: identifying the distinct units of an acoustic sequence, describing the different ways that information can be contained within a sequence, and analysing the structure of that sequence. Each of these sections is further subdivided to address the key questions and approaches in that area. We propose a uniform, systematic, and comprehensive approach to studying sequences, with the goal of clarifying research terms used in different fields, and facilitating collaboration and comparative studies. Allowing greater interdisciplinary collaboration will facilitate the investigation of many important questions in the evolution of communication and sociality.
Thu, 23 Mar 2017 08:55:32 GMThttp://hdl.handle.net/2117/1028162017-03-23T08:55:32ZKershenbaum, ArikBlumstein, Daniel T.Roch, Marie A.Ferrer Cancho, RamonAnimal acoustic communication often takes the form of complex sequences, made up of multiple distinct acoustic units. Apart from the well-known example of birdsong, other animals such as insects, amphibians, and mammals (including bats, rodents, primates, and cetaceans) also generate complex acoustic sequences. Occasionally, such as with birdsong, the adaptive role of these sequences seems clear (e.g. mate attraction and territorial defence). More often however, researchers have only begun to characterise-let alone understand-the significance and meaning of acoustic sequences. Hypotheses abound, but there is little agreement as to how sequences should be defined and analysed. Our review aims to outline suitable methods for testing these hypotheses, and to describe the major limitations to our current and near-future knowledge on questions of acoustic sequences. This review and prospectus is the result of a collaborative effort between 43 scientists from the fields of animal behaviour, ecology and evolution, signal processing, machine learning, quantitative linguistics, and information theory, who gathered for a 2013 workshop entitled, 'Analysing vocal sequences in animals'. Our goal is to present not just a review of the state of the art, but to propose a methodological framework that summarises what we suggest are the best practices for research in this field, across taxa and across disciplines. We also provide a tutorial-style introduction to some of the most promising algorithmic approaches for analysing sequences. We divide our review into three sections: identifying the distinct units of an acoustic sequence, describing the different ways that information can be contained within a sequence, and analysing the structure of that sequence. Each of these sections is further subdivided to address the key questions and approaches in that area. We propose a uniform, systematic, and comprehensive approach to studying sequences, with the goal of clarifying research terms used in different fields, and facilitating collaboration and comparative studies. Allowing greater interdisciplinary collaboration will facilitate the investigation of many important questions in the evolution of communication and sociality.