Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3974
Tue, 28 Feb 2017 08:13:49 GMT2017-02-28T08:13:49ZPartial match queries in relaxed K-dt trees
http://hdl.handle.net/2117/101520
Partial match queries in relaxed K-dt trees
Duch Brown, Amalia; Lau Laynes-Lozada, Gustavo Salvador
The study of partial match queries on random hierarchical multidimensional data structures dates back to Ph. Flajolet and C. Puech’s 1986 seminal paper on partial match retrieval. It was not until recently that fixed (as opposed to random) partial match queries were studied for random relaxed K-d trees, random standard K-d trees, and random 2-dimensional quad trees. Based on those results it seemed
natural to classify the general form of the cost of fixed partial match queries into two families: that of either random hierarchical structures or perfectly balanced structures, as conjectured by Duch, Lau and Martínez (On the Cost of Fixed Partial Queries in K-d trees Algorithmica, 75(4):684–723, 2016). Here we show that the conjecture just mentioned does not hold by introducing relaxed K-dt trees and providing the average-case analysis for random partial match queries as well as some advances on the average-case analysis for fixed partial match queries on them. In fact this cost –for fixed partial match queries– does not follow the conjectured forms.
Fri, 24 Feb 2017 10:27:25 GMThttp://hdl.handle.net/2117/1015202017-02-24T10:27:25ZDuch Brown, AmaliaLau Laynes-Lozada, Gustavo SalvadorThe study of partial match queries on random hierarchical multidimensional data structures dates back to Ph. Flajolet and C. Puech’s 1986 seminal paper on partial match retrieval. It was not until recently that fixed (as opposed to random) partial match queries were studied for random relaxed K-d trees, random standard K-d trees, and random 2-dimensional quad trees. Based on those results it seemed
natural to classify the general form of the cost of fixed partial match queries into two families: that of either random hierarchical structures or perfectly balanced structures, as conjectured by Duch, Lau and Martínez (On the Cost of Fixed Partial Queries in K-d trees Algorithmica, 75(4):684–723, 2016). Here we show that the conjecture just mentioned does not hold by introducing relaxed K-dt trees and providing the average-case analysis for random partial match queries as well as some advances on the average-case analysis for fixed partial match queries on them. In fact this cost –for fixed partial match queries– does not follow the conjectured forms.Mining structured Petri nets for the visualization of process behavior
http://hdl.handle.net/2117/100797
Mining structured Petri nets for the visualization of process behavior
San Pedro Martín, Javier de; Cortadella Fortuny, Jordi
Visualization is essential for understanding the models obtained by process mining. Clear and efficient visual representations make the embedded information more accessible and analyzable. This work presents a novel approach for generating process models with structural properties that induce visually friendly layouts. Rather than generating a single model that captures all behaviors, a set of Petri net models is delivered, each one covering a subset of traces of the log. The models are mined by extracting slices of labelled transition systems with specific properties from the complete state space produced by the process logs. In most cases, few Petri nets are sufficient to cover a significant part of the behavior produced by the log.
Fri, 10 Feb 2017 08:35:24 GMThttp://hdl.handle.net/2117/1007972017-02-10T08:35:24ZSan Pedro Martín, Javier deCortadella Fortuny, JordiVisualization is essential for understanding the models obtained by process mining. Clear and efficient visual representations make the embedded information more accessible and analyzable. This work presents a novel approach for generating process models with structural properties that induce visually friendly layouts. Rather than generating a single model that captures all behaviors, a set of Petri net models is delivered, each one covering a subset of traces of the log. The models are mined by extracting slices of labelled transition systems with specific properties from the complete state space produced by the process logs. In most cases, few Petri nets are sufficient to cover a significant part of the behavior produced by the log.Comparing MapReduce and pipeline implementations for counting triangles
http://hdl.handle.net/2117/100579
Comparing MapReduce and pipeline implementations for counting triangles
Pasarella Sánchez, Ana Edelmira; Vidal Serodio, Maria Esther; Zoltan, Cristina
A generalized method to define the Divide & Conquer paradigm in order to have processors acting on its own data and scheduled in a
parallel fashion. MapReduce is a programming model that follows this paradigm, and allows for the definition of efficient solutions by both decomposing a problem into steps on subsets of the input data
and combining the results of each step to produce final results. Albeit used for the implementation of a wide variety of computational problems, MapReduce performance can be negatively affected
whenever the replication factor grows or the size of the input is larger than the resources available at each processor. In this paper we show an alternative approach to implement the Divide & Conquer
paradigm, named pipeline. The main features of pipeline are illustrated on a parallel implementation of the well-known problem of counting triangles in a graph. This problem is especially interesting either when the input graph does not fit in memory or is dynamically generated. To evaluate the properties of pipeline, a dynamic pipeline of processes and an ad-hoc version of MapReduce are implemented in the language Go, exploiting its ability to deal with channels and spawned processes.
An empirical evaluation is conducted on graphs of different sizes and densities. Observed results suggest that pipeline allows for the implementation of an efficient solution of the problem of counting
triangles in a graph, particularly, in dense and large graphs, drastically reducing the execution time with respect to the MapReduce implementation.
Mon, 06 Feb 2017 08:48:11 GMThttp://hdl.handle.net/2117/1005792017-02-06T08:48:11ZPasarella Sánchez, Ana EdelmiraVidal Serodio, Maria EstherZoltan, CristinaA generalized method to define the Divide & Conquer paradigm in order to have processors acting on its own data and scheduled in a
parallel fashion. MapReduce is a programming model that follows this paradigm, and allows for the definition of efficient solutions by both decomposing a problem into steps on subsets of the input data
and combining the results of each step to produce final results. Albeit used for the implementation of a wide variety of computational problems, MapReduce performance can be negatively affected
whenever the replication factor grows or the size of the input is larger than the resources available at each processor. In this paper we show an alternative approach to implement the Divide & Conquer
paradigm, named pipeline. The main features of pipeline are illustrated on a parallel implementation of the well-known problem of counting triangles in a graph. This problem is especially interesting either when the input graph does not fit in memory or is dynamically generated. To evaluate the properties of pipeline, a dynamic pipeline of processes and an ad-hoc version of MapReduce are implemented in the language Go, exploiting its ability to deal with channels and spawned processes.
An empirical evaluation is conducted on graphs of different sizes and densities. Observed results suggest that pipeline allows for the implementation of an efficient solution of the problem of counting
triangles in a graph, particularly, in dense and large graphs, drastically reducing the execution time with respect to the MapReduce implementation.Computational coverage of type logical grammar: The Montague test
http://hdl.handle.net/2117/100544
Computational coverage of type logical grammar: The Montague test
Morrill, Glyn; Valentín Fernández Gallart, José Oriol
It is nearly half a century since Montague made his contributions to
the field of logical semantics. In this time, computational linguistics has taken an almost entirely statistical turn and mainstream linguistics has adopted an almost entirely non-formal methodology. But in a minority approach reaching back before the linguistic revolution, and to the origins of computing, type logical grammar (TLG) has continued championing the flags of symbolic computation and logical rigor in discrete grammar. In this paper, we aim to concretise a measure
of progress for computational grammar in the form of the Montague Test. This is the challenge of providing a computational cover grammar of the Montague fragment. We formulate this Montague Test and show how the challenge is met by the type logical parser/theorem-prover CatLog2.
Fri, 03 Feb 2017 11:52:28 GMThttp://hdl.handle.net/2117/1005442017-02-03T11:52:28ZMorrill, GlynValentín Fernández Gallart, José OriolIt is nearly half a century since Montague made his contributions to
the field of logical semantics. In this time, computational linguistics has taken an almost entirely statistical turn and mainstream linguistics has adopted an almost entirely non-formal methodology. But in a minority approach reaching back before the linguistic revolution, and to the origins of computing, type logical grammar (TLG) has continued championing the flags of symbolic computation and logical rigor in discrete grammar. In this paper, we aim to concretise a measure
of progress for computational grammar in the form of the Montague Test. This is the challenge of providing a computational cover grammar of the Montague fragment. We formulate this Montague Test and show how the challenge is met by the type logical parser/theorem-prover CatLog2.A comparative study of navigation meshes
http://hdl.handle.net/2117/100494
A comparative study of navigation meshes
Van Toll, Wouter; Triesscheijn, Roy; Kallmann, Marcello; Oliva Martínez, Ramon; Pelechano Gómez, Núria; Pettré, Julien; Geraerts, Roland
A navigation mesh is a representation of a 2D or 3D virtual environment that enables path planning and crowd simulation for walking characters. Various state-of-the-art navigation meshes exist, but there is no standardized way of evaluating or comparing them. Each implementation is in a different state of maturity, has been tested on different hardware, uses different example environments, and may have been designed with a different application in mind.
In this paper, we conduct the first comparative study of navigation meshes. First, we give general definitions of 2D and 3D environments and navigation meshes. Second, we propose theoretical properties by which navigation meshes can be classified. Third, we introduce metrics by which the quality of a navigation mesh implementation can be measured objectively. Finally, we use these metrics to compare various state-of-the-art navigation meshes in a range of 2D and 3D environments.
We expect that this work will set a new standard for the evaluation of navigation meshes, that it will help developers choose an appropriate navigation mesh for their application, and that it will steer future research on navigation meshes in interesting directions.
Thu, 02 Feb 2017 14:26:23 GMThttp://hdl.handle.net/2117/1004942017-02-02T14:26:23ZVan Toll, WouterTriesscheijn, RoyKallmann, MarcelloOliva Martínez, RamonPelechano Gómez, NúriaPettré, JulienGeraerts, RolandA navigation mesh is a representation of a 2D or 3D virtual environment that enables path planning and crowd simulation for walking characters. Various state-of-the-art navigation meshes exist, but there is no standardized way of evaluating or comparing them. Each implementation is in a different state of maturity, has been tested on different hardware, uses different example environments, and may have been designed with a different application in mind.
In this paper, we conduct the first comparative study of navigation meshes. First, we give general definitions of 2D and 3D environments and navigation meshes. Second, we propose theoretical properties by which navigation meshes can be classified. Third, we introduce metrics by which the quality of a navigation mesh implementation can be measured objectively. Finally, we use these metrics to compare various state-of-the-art navigation meshes in a range of 2D and 3D environments.
We expect that this work will set a new standard for the evaluation of navigation meshes, that it will help developers choose an appropriate navigation mesh for their application, and that it will steer future research on navigation meshes in interesting directions.The death star challenge: an ambitious and motivating engineering project to promote astronautics and transform society's vision about space research
http://hdl.handle.net/2117/100477
The death star challenge: an ambitious and motivating engineering project to promote astronautics and transform society's vision about space research
Pérez Poch, Antoni; Sánchez Carracedo, Fermín; López Álvarez, David; Alier Forment, Marc
The race to put a person on the Moon motivated and captivated the imagination of USA society and the community
worldwide. This led to an unprecedented investment in science, technology and the space program, which eventually
resulted in a successful Moon landing in 1969. Current estimations state that, for every dollar invested in space
technology, there is a return of more than five dollars for the country's GDP. However, public opinion worldwide
does not perceive this investment as a benefit for the society. The moonshot was a challenge, an idea, a dream that
aligned a whole society towards progress. To change society's vision about space, our proposal is to promote an
outrageously ambitious, exciting and motivating Engineering project. While this project may be extremely difficult
to implement, it can be envisioned, brainstormed, analyzed, and even brought to the attention of policy makers.
It would involve the design of the greatest Engineering work in space, even greater than the International Space
Station (ISS). This endeavor would also help to raise awareness in our society about the Earth's sustainability. To
that end, the project would drive a circular economy requiring the development of technologies that in the mid-term
would reverse climate change. We believe that involving students from different backgrounds in this project would
be vital to attract the interest of future generations in Aeronautics and Space research. In order to do this, we propose
a number of outreach activities at all different teaching levels. We also propose the organization of an international
contest for different ages, in which student groups would submit innovative proposals for different technologies that
would be developed throughout the project. Furthermore, in order to raise awareness in our society, the project
should generate a debate.
The project would consist of the design and construction of a Space Station similar to that of the Star Wars “Death
Star”, but without its weaponry and making the most of the publicity around and the revived interest in the Star Wars
movies. Its construction would be feasible within a reasonable period of time, and the design would involve
international, intercultural and multidisciplinary student teams. This paper outlines the principles that underpin the
viability of this project. It also proposes a communication plan for universities as well as an outreach plan for the
public at large. Finally, it defines a strategy for developing sustainable projects and assessing the students' learning
outcomes.
Thu, 02 Feb 2017 09:55:19 GMThttp://hdl.handle.net/2117/1004772017-02-02T09:55:19ZPérez Poch, AntoniSánchez Carracedo, FermínLópez Álvarez, DavidAlier Forment, MarcThe race to put a person on the Moon motivated and captivated the imagination of USA society and the community
worldwide. This led to an unprecedented investment in science, technology and the space program, which eventually
resulted in a successful Moon landing in 1969. Current estimations state that, for every dollar invested in space
technology, there is a return of more than five dollars for the country's GDP. However, public opinion worldwide
does not perceive this investment as a benefit for the society. The moonshot was a challenge, an idea, a dream that
aligned a whole society towards progress. To change society's vision about space, our proposal is to promote an
outrageously ambitious, exciting and motivating Engineering project. While this project may be extremely difficult
to implement, it can be envisioned, brainstormed, analyzed, and even brought to the attention of policy makers.
It would involve the design of the greatest Engineering work in space, even greater than the International Space
Station (ISS). This endeavor would also help to raise awareness in our society about the Earth's sustainability. To
that end, the project would drive a circular economy requiring the development of technologies that in the mid-term
would reverse climate change. We believe that involving students from different backgrounds in this project would
be vital to attract the interest of future generations in Aeronautics and Space research. In order to do this, we propose
a number of outreach activities at all different teaching levels. We also propose the organization of an international
contest for different ages, in which student groups would submit innovative proposals for different technologies that
would be developed throughout the project. Furthermore, in order to raise awareness in our society, the project
should generate a debate.
The project would consist of the design and construction of a Space Station similar to that of the Star Wars “Death
Star”, but without its weaponry and making the most of the publicity around and the revived interest in the Star Wars
movies. Its construction would be feasible within a reasonable period of time, and the design would involve
international, intercultural and multidisciplinary student teams. This paper outlines the principles that underpin the
viability of this project. It also proposes a communication plan for universities as well as an outreach plan for the
public at large. Finally, it defines a strategy for developing sustainable projects and assessing the students' learning
outcomes.Improving ontological knowledge with reinforcement methods in recommendation of the best data mining method for a real environmental problem
http://hdl.handle.net/2117/100455
Improving ontological knowledge with reinforcement methods in recommendation of the best data mining method for a real environmental problem
Gibert, Karina; Sànchez-Marrè, Miquel
There are many data mining techniques available for a user wishing to discover some model from her/his data. This diversi ty can cause some trou- bles to the final non - expert users, who often do not have a clear idea of what are the available methods, and frequently have doubts about the most suitable method for a concrete problem in a domain. In previous works, prior ontologi- c al knowledge about data mining methods has been used to describe the main characteristics of a collection of methods and to filter which methods are suita- ble or not for a given real data mining problem, by matching their characteris- tics with those hold in the target dataset. In this paper, the concept of rein- forcement tables is introduced to move to a multi - criteria scenario in which a measure of relevance is computed for every method . A contribution of the work is to develop an open - frame where both the characteristics of methods consid- ered in the reference ontology and the reinforcement tables may evolve along time according to changes in the methodological state of the art, going beyond classical expert systems. The paper introduces the formal framework and some examples to illustrate the performance of the proposal.
Wed, 01 Feb 2017 12:33:26 GMThttp://hdl.handle.net/2117/1004552017-02-01T12:33:26ZGibert, KarinaSànchez-Marrè, MiquelThere are many data mining techniques available for a user wishing to discover some model from her/his data. This diversi ty can cause some trou- bles to the final non - expert users, who often do not have a clear idea of what are the available methods, and frequently have doubts about the most suitable method for a concrete problem in a domain. In previous works, prior ontologi- c al knowledge about data mining methods has been used to describe the main characteristics of a collection of methods and to filter which methods are suita- ble or not for a given real data mining problem, by matching their characteris- tics with those hold in the target dataset. In this paper, the concept of rein- forcement tables is introduced to move to a multi - criteria scenario in which a measure of relevance is computed for every method . A contribution of the work is to develop an open - frame where both the characteristics of methods consid- ered in the reference ontology and the reinforcement tables may evolve along time according to changes in the methodological state of the art, going beyond classical expert systems. The paper introduces the formal framework and some examples to illustrate the performance of the proposal.A semantics of business configurations using symbolic graphs
http://hdl.handle.net/2117/100385
A semantics of business configurations using symbolic graphs
Mylonakis Pascual, Nicolás; Orejas Valdés, Fernando; Fiadeiro, José Luiz
In this paper we give graph-semantics to a fundamental part of the semantics of the service modeling language SRML: business configurations. To achieve this goal we use symbolic graph transformation systems. We formalize the semantics using this graph transformation system and illustrating it with a simple running example of a trip booking agent.
Tue, 31 Jan 2017 13:43:47 GMThttp://hdl.handle.net/2117/1003852017-01-31T13:43:47ZMylonakis Pascual, NicolásOrejas Valdés, FernandoFiadeiro, José LuizIn this paper we give graph-semantics to a fundamental part of the semantics of the service modeling language SRML: business configurations. To achieve this goal we use symbolic graph transformation systems. We formalize the semantics using this graph transformation system and illustrating it with a simple running example of a trip booking agent.Conditions for compatibility of components: The case of masters and slaves
http://hdl.handle.net/2117/100199
Conditions for compatibility of components: The case of masters and slaves
Beek, Maurice ter; Carmona Vargas, Josep; Kleijn, Jetty
We consider systems composed of reactive components that collaborate through synchronised execution of common actions. These multi-component systems are formally represented as team automata, a model that allows a wide spectrum of synchronisation policies to combine components into higher-level systems. We investigate the
correct-by-construction engineering of such systems of systems from the point of view of correct communications between the components (no message loss or deadlocks due to indefinite waiting). This leads to a proposal for a generic definition of compatibility of components relative to the adopted synchronisation policy. This definition appears
to be particularly appropriate for so-called master-slave synchronisations by which input actions (for `slaves') are driven
by output actions (from `masters').
Fri, 27 Jan 2017 12:09:50 GMThttp://hdl.handle.net/2117/1001992017-01-27T12:09:50ZBeek, Maurice terCarmona Vargas, JosepKleijn, JettyWe consider systems composed of reactive components that collaborate through synchronised execution of common actions. These multi-component systems are formally represented as team automata, a model that allows a wide spectrum of synchronisation policies to combine components into higher-level systems. We investigate the
correct-by-construction engineering of such systems of systems from the point of view of correct communications between the components (no message loss or deadlocks due to indefinite waiting). This leads to a proposal for a generic definition of compatibility of components relative to the adopted synchronisation policy. This definition appears
to be particularly appropriate for so-called master-slave synchronisations by which input actions (for `slaves') are driven
by output actions (from `masters').Non-homogenizable classes of finite structures
http://hdl.handle.net/2117/100189
Non-homogenizable classes of finite structures
Atserias, Albert; Torunczyk, Szymon Abram
Homogenization is a powerful way of taming a class of finite structures with several interesting applications in different areas, from Ramsey theory in combinatorics to constraint satisfaction problems (CSPs) in computer science, through (finite) model theory. A few sufficient conditions for a class of finite structures to allow homogenization are known, and here we provide a necessary condition. This lets us show that certain natural classes are not homogenizable: 1) the class of locally consistent systems of linear equations over the two-element field or any finite Abelian group, and 2) the class of finite structures that forbid homomorphisms from a specific MSO-definable class of structures of treewidth two. In combination with known results, the first example shows that, up to pp-interpretability, the CSPs that are solvable by local consistency methods are distinguished from the rest by the fact that their classes of locally consistent instances are homogenizable. The second example shows that, for MSO-definable classes of forbidden patterns, treewidth one versus two is the dividing line to homogenizability.
Fri, 27 Jan 2017 10:51:13 GMThttp://hdl.handle.net/2117/1001892017-01-27T10:51:13ZAtserias, AlbertTorunczyk, Szymon AbramHomogenization is a powerful way of taming a class of finite structures with several interesting applications in different areas, from Ramsey theory in combinatorics to constraint satisfaction problems (CSPs) in computer science, through (finite) model theory. A few sufficient conditions for a class of finite structures to allow homogenization are known, and here we provide a necessary condition. This lets us show that certain natural classes are not homogenizable: 1) the class of locally consistent systems of linear equations over the two-element field or any finite Abelian group, and 2) the class of finite structures that forbid homomorphisms from a specific MSO-definable class of structures of treewidth two. In combination with known results, the first example shows that, up to pp-interpretability, the CSPs that are solvable by local consistency methods are distinguished from the rest by the fact that their classes of locally consistent instances are homogenizable. The second example shows that, for MSO-definable classes of forbidden patterns, treewidth one versus two is the dividing line to homogenizability.