Departament de Ciències de la Computació
http://hdl.handle.net/2117/3971
2017-01-21T03:04:27ZProcess model comparison based on cophenetic distance
http://hdl.handle.net/2117/99744
Process model comparison based on cophenetic distance
Sánchez Charles, David; Muntés Mulero, Víctor; Carmona Vargas, Josep; Solé, Marc
The automated comparison of process models has received increasing attention in the last decade, due to the growing existence of process models and repositories, and the consequent need to assess similarities between the underlying processes. Current techniques for process model comparison are either structural (based on graph edit
distances), or behavioural (through activity profiles or the analysis of the execution semantics). Accordingly, there is a gap between the quality of the information provided by these two families, i.e., structural techniques may be fast but inaccurate, whilst behavioural are accurate but complex. In this paper we present a novel technique, that is based on a well-known technique to compare labeled trees through the notion of Cophenetic distance. The technique lays between
the two families of methods for comparing a process model: it has an structural nature, but can provide accurate information on the differences/similarities of two process models. The experimental evaluation on various benchmarks sets are reported, that position the proposed technique as a valuable tool for process model comparison.
2017-01-20T10:35:50ZSánchez Charles, DavidMuntés Mulero, VíctorCarmona Vargas, JosepSolé, MarcThe automated comparison of process models has received increasing attention in the last decade, due to the growing existence of process models and repositories, and the consequent need to assess similarities between the underlying processes. Current techniques for process model comparison are either structural (based on graph edit
distances), or behavioural (through activity profiles or the analysis of the execution semantics). Accordingly, there is a gap between the quality of the information provided by these two families, i.e., structural techniques may be fast but inaccurate, whilst behavioural are accurate but complex. In this paper we present a novel technique, that is based on a well-known technique to compare labeled trees through the notion of Cophenetic distance. The technique lays between
the two families of methods for comparing a process model: it has an structural nature, but can provide accurate information on the differences/similarities of two process models. The experimental evaluation on various benchmarks sets are reported, that position the proposed technique as a valuable tool for process model comparison.Narrow proofs may be maximally long
http://hdl.handle.net/2117/99737
Narrow proofs may be maximally long
Atserias, Albert; Lauria, Massimo; Nordström, Jakob
We prove that there are 3-CNF formulas over n variables that can be refuted in resolution in width w but require resolution proofs of size n(Omega(w)). This shows that the simple counting argument that any formula refutable in width w must have a proof in size n(O(w)) is essentially tight. Moreover, our lower bound generalizes to polynomial calculus resolution and Sherali-Adams, implying that the corresponding size upper bounds in terms of degree and rank are tight as well. The lower bound does not extend all the way to Lasserre, however, since we show that there the formulas we study have proofs of constant rank and size polynomial in both n and w.
2017-01-20T08:41:23ZAtserias, AlbertLauria, MassimoNordström, JakobWe prove that there are 3-CNF formulas over n variables that can be refuted in resolution in width w but require resolution proofs of size n(Omega(w)). This shows that the simple counting argument that any formula refutable in width w must have a proof in size n(O(w)) is essentially tight. Moreover, our lower bound generalizes to polynomial calculus resolution and Sherali-Adams, implying that the corresponding size upper bounds in terms of degree and rank are tight as well. The lower bound does not extend all the way to Lasserre, however, since we show that there the formulas we study have proofs of constant rank and size polynomial in both n and w.Diseño del posgrado STEM de formación del profesorado ICE-UPC basado en competencias
http://hdl.handle.net/2117/99689
Diseño del posgrado STEM de formación del profesorado ICE-UPC basado en competencias
López Álvarez, David; Pérez Poch, Antoni; Adam Salvatierra, Araceli; Delgado García, María José
In this paper we describe a higher education teacher training programme developed by the Institute of Education Sciences of our university (Universitat Politècnica de Catalunya · BarcelonaTech). The methodology for designing the programme was based on identifying the skills that a teacher should develop and analyzing previous training programmes. Finally, we analyse the first results obtained from the teaching of this programme.; Este artículo se incluye en un proyecto de la Universitat Politècnica de
Catalunya para implementar un programa de formación del profesorado universitario
basado en las competencias del mismo. El proceso se realiza a partir del análisis de las
competencias docentes: tras estudiar con anterioridad qué competencias debería
tener un docente e implementar una primera versión del programa de formación, se
diseña la estructura del programa y se analizan los primeros resultados de su
impartición.
2017-01-19T13:15:21ZLópez Álvarez, DavidPérez Poch, AntoniAdam Salvatierra, AraceliDelgado García, María JoséIn this paper we describe a higher education teacher training programme developed by the Institute of Education Sciences of our university (Universitat Politècnica de Catalunya · BarcelonaTech). The methodology for designing the programme was based on identifying the skills that a teacher should develop and analyzing previous training programmes. Finally, we analyse the first results obtained from the teaching of this programme.
Este artículo se incluye en un proyecto de la Universitat Politècnica de
Catalunya para implementar un programa de formación del profesorado universitario
basado en las competencias del mismo. El proceso se realiza a partir del análisis de las
competencias docentes: tras estudiar con anterioridad qué competencias debería
tener un docente e implementar una primera versión del programa de formación, se
diseña la estructura del programa y se analizan los primeros resultados de su
impartición.Firefighting as a strategic game
http://hdl.handle.net/2117/99674
Firefighting as a strategic game
Álvarez Faura, M. del Carme; Blesa Aguilera, Maria Josep; Molter, Hendrik
The Firefighter Problem was proposed in 1995 as a deterministic discrete-time model for the spread and containment of a fire. The problem is defined on an undirected finite graph G = (V, E), where fire breaks out initially at f nodes. In each subsequent time-step, two actions occur: a certain number b of firefighters are placed on nonburning nodes, permanently protecting them from the fire, then the fire spreads to all nondefended neighbors of the nodes on fire. Because the graph is finite, at some point each node is either on fire or saved, and thus the fire cannot spread further. One of the objectives for the problem is to place the firefighters in such a way that the number of saved nodes is maximized. The applications of the Firefighter Problem reach from real fires to the spreading of diseases and the containment of floods. Furthermore, it can be used to model the spread of computer viruses or viral marketing in communication networks. Most research on the problem considers the case in which the fire starts in a single place (i.e., f = 1), and in which the budget of available firefighters per time-step is one (i.e., b = 1). So does the work in this study. This configuration already leads to hard problems and, even in this case, the problem is known to be NP-hard. In this work, we study the problem from a game-theoretical perspective. We introduce a strategic game model for the Firefighter Problem to tackle its complexity from a different angle. We refer to it as the Firefighter Game. Such a game-based context seems very appropriate when applied to large networks where entities may act and make decisions based on their own interests, without global coordination. At every time-step of the game, a player decides whether to place a new firefighter in a nonburning node of the graph. If so, he must decide where to place it. By placing it, the player is indirectly deciding which nodes to protect at that time-step. We define different utility functions in order to model selfish and nonselfish scenarios, which lead to equivalent games. We show that the Price of Anarchy (PoA) is linear for a particular family of graphs, but it is at most two for trees. We also analyze the quality of the equilibria when coalitions among players are allowed. It turns out that it is possible to compute an equilibrium in polynomial time, even for constant-size coalitions. This yields to a polynomial time approximation algorithm for the problem and its approximation ratio equals the PoA of the corresponding game. We show that for some specific topologies, the PoA is constant when constant-size coalitions are considered.
2017-01-19T12:21:27ZÁlvarez Faura, M. del CarmeBlesa Aguilera, Maria JosepMolter, HendrikThe Firefighter Problem was proposed in 1995 as a deterministic discrete-time model for the spread and containment of a fire. The problem is defined on an undirected finite graph G = (V, E), where fire breaks out initially at f nodes. In each subsequent time-step, two actions occur: a certain number b of firefighters are placed on nonburning nodes, permanently protecting them from the fire, then the fire spreads to all nondefended neighbors of the nodes on fire. Because the graph is finite, at some point each node is either on fire or saved, and thus the fire cannot spread further. One of the objectives for the problem is to place the firefighters in such a way that the number of saved nodes is maximized. The applications of the Firefighter Problem reach from real fires to the spreading of diseases and the containment of floods. Furthermore, it can be used to model the spread of computer viruses or viral marketing in communication networks. Most research on the problem considers the case in which the fire starts in a single place (i.e., f = 1), and in which the budget of available firefighters per time-step is one (i.e., b = 1). So does the work in this study. This configuration already leads to hard problems and, even in this case, the problem is known to be NP-hard. In this work, we study the problem from a game-theoretical perspective. We introduce a strategic game model for the Firefighter Problem to tackle its complexity from a different angle. We refer to it as the Firefighter Game. Such a game-based context seems very appropriate when applied to large networks where entities may act and make decisions based on their own interests, without global coordination. At every time-step of the game, a player decides whether to place a new firefighter in a nonburning node of the graph. If so, he must decide where to place it. By placing it, the player is indirectly deciding which nodes to protect at that time-step. We define different utility functions in order to model selfish and nonselfish scenarios, which lead to equivalent games. We show that the Price of Anarchy (PoA) is linear for a particular family of graphs, but it is at most two for trees. We also analyze the quality of the equilibria when coalitions among players are allowed. It turns out that it is possible to compute an equilibrium in polynomial time, even for constant-size coalitions. This yields to a polynomial time approximation algorithm for the problem and its approximation ratio equals the PoA of the corresponding game. We show that for some specific topologies, the PoA is constant when constant-size coalitions are considered.A multi-projector CAVE system with commodity hardware and gesture-based interaction
http://hdl.handle.net/2117/99668
A multi-projector CAVE system with commodity hardware and gesture-based interaction
Andújar Gran, Carlos Antonio; Brunet Crosa, Pere; Vinacua Pla, Álvaro; Vico Moya, Miguel Ángel; Díaz García, Jesús
Spatially-immersive systems such as CAVEs provide users with surrounding worlds by projecting 3D models on multiple screens around the viewer. Compared to alternative immersive systems such as HMDs, CAVE systems are a powerful tool for collaborative inspection of virtual environments due to better use of peripheral vision, less sensitivity to tracking errors, and higher communication possibilities among users. Unfortunately, traditional CAVE setups require sophisticated equipment including stereo-ready projectors and tracking systems with high acquisition and maintenance costs. In this paper we present the design and construction of a passive-stereo, four-wall CAVE system based on commodity hardware. Our system works with any mix of a wide range of projector models that can be replaced independently at any time, and achieves high resolution and brightness at a minimum cost. The key ingredients of our CAVE are a self-calibration approach that guarantees continuity across the screen, as well as a gesture-based interaction approach based on a clever
combination of skeletal data from multiple Kinect sensors.
2017-01-19T11:55:25ZAndújar Gran, Carlos AntonioBrunet Crosa, PereVinacua Pla, ÁlvaroVico Moya, Miguel ÁngelDíaz García, JesúsSpatially-immersive systems such as CAVEs provide users with surrounding worlds by projecting 3D models on multiple screens around the viewer. Compared to alternative immersive systems such as HMDs, CAVE systems are a powerful tool for collaborative inspection of virtual environments due to better use of peripheral vision, less sensitivity to tracking errors, and higher communication possibilities among users. Unfortunately, traditional CAVE setups require sophisticated equipment including stereo-ready projectors and tracking systems with high acquisition and maintenance costs. In this paper we present the design and construction of a passive-stereo, four-wall CAVE system based on commodity hardware. Our system works with any mix of a wide range of projector models that can be replaced independently at any time, and achieves high resolution and brightness at a minimum cost. The key ingredients of our CAVE are a self-calibration approach that guarantees continuity across the screen, as well as a gesture-based interaction approach based on a clever
combination of skeletal data from multiple Kinect sensors.An experimental study on the effects of shading in 3D perception of volumetric models
http://hdl.handle.net/2117/99662
An experimental study on the effects of shading in 3D perception of volumetric models
Díaz Iriberri, José; Ropinski, Timo; Navazo Álvaro, Isabel; Gobbetti, Enrico; Vázquez Alcocer, Pere Pau
Throughout the years, many shading techniques have been developed to improve the conveying of information in volume visualization. Some of these methods, usually referred to as realistic, are supposed to provide better cues for the understanding of volume data sets. While shading approaches are heavily exploited in traditional monoscopic setups, no previous study has analyzed the effect of these techniques in virtual reality. To further explore the influence of shading on the understanding of volume data in such environments, we carried out a user study in a desktop-based stereoscopic setup. The goals of the study were to investigate the impact of well-known shading approaches and the influence of real illumination on depth perception. Participants had to perform three different perceptual tasks when exposed to static visual stimuli. 45 participants took part in the study, giving us 1152 trials for each task. Results show that advanced shading techniques improve depth perception in stereoscopic volume visualization. As well, external lighting does not affect depth perception when these shading methods are applied. As a result, we derive some guidelines that may help the researchers when selecting illumination models for stereoscopic rendering.
2017-01-19T09:54:00ZDíaz Iriberri, JoséRopinski, TimoNavazo Álvaro, IsabelGobbetti, EnricoVázquez Alcocer, Pere PauThroughout the years, many shading techniques have been developed to improve the conveying of information in volume visualization. Some of these methods, usually referred to as realistic, are supposed to provide better cues for the understanding of volume data sets. While shading approaches are heavily exploited in traditional monoscopic setups, no previous study has analyzed the effect of these techniques in virtual reality. To further explore the influence of shading on the understanding of volume data in such environments, we carried out a user study in a desktop-based stereoscopic setup. The goals of the study were to investigate the impact of well-known shading approaches and the influence of real illumination on depth perception. Participants had to perform three different perceptual tasks when exposed to static visual stimuli. 45 participants took part in the study, giving us 1152 trials for each task. Results show that advanced shading techniques improve depth perception in stereoscopic volume visualization. As well, external lighting does not affect depth perception when these shading methods are applied. As a result, we derive some guidelines that may help the researchers when selecting illumination models for stereoscopic rendering.Projecte Inspira'ns: detecció d'idees relacionades
http://hdl.handle.net/2117/99488
Projecte Inspira'ns: detecció d'idees relacionades
Vigo, M.
El projecte Inspira'ns compta amb un sistema online per a la recollida de suggeriments i comentaris (Idea) d'usuaris. Aquests comentaris es classifiquen per categories (Aplicacions mòbils, Banca mòbil, Banca per Internet, Caixers i Targetes), i pels temes que tracten (el tema és lliure, generalment es tracta de peticions de millora d'un servei o problemes detectats amb algun producte o servei, entre d'altres). Sovint els usuaris es refereixen a una mateixa Idea, és a dir, es reben suggeriments i comentaris repetits. Actualment, la classificació d'aquestes idees es duu a terme de forma manual. L'objectiu d'aquest projecte és desenvolupar una metodologia que permeti detectar que una nova Idea és similar a una Idea anterior rebuda. És a dir, donat un conjunt D d'idees, determinar si una nova Idea d està relacionada (és similar) amb alguna de les idees del conjunt D.
2017-01-17T14:03:35ZVigo, M.El projecte Inspira'ns compta amb un sistema online per a la recollida de suggeriments i comentaris (Idea) d'usuaris. Aquests comentaris es classifiquen per categories (Aplicacions mòbils, Banca mòbil, Banca per Internet, Caixers i Targetes), i pels temes que tracten (el tema és lliure, generalment es tracta de peticions de millora d'un servei o problemes detectats amb algun producte o servei, entre d'altres). Sovint els usuaris es refereixen a una mateixa Idea, és a dir, es reben suggeriments i comentaris repetits. Actualment, la classificació d'aquestes idees es duu a terme de forma manual. L'objectiu d'aquest projecte és desenvolupar una metodologia que permeti detectar que una nova Idea és similar a una Idea anterior rebuda. És a dir, donat un conjunt D d'idees, determinar si una nova Idea d està relacionada (és similar) amb alguna de les idees del conjunt D.A reply to Kubota and Levine on gapping
http://hdl.handle.net/2117/99487
A reply to Kubota and Levine on gapping
Valentín Fernández Gallart, José Oriol; Morrill, Glyn
In a series of papers Kubota and Levine give an account of gapping and determiner gapping in terms of hybrid type logical grammar, including anomalous scopal interactions with auxiliaries and negative quantifiers. We make three observations: i) under the counterpart assumptions that Kubota and Levine make, the existent displacement type logical grammar account of gapping already accounts for the scopal interactions, ii) Kubota and Levine overgenerate determiner-verb order permutations in determiner gapping conjuncts whereas the immediate adaptation of their proposal to displacement type logical grammar does not do so, and iii) Kubota and Levine do not capture simplex gapping as a special case of complex gapping, but require distinct lexical entries for the two cases; we show how a generalisation of displacement type logical grammar allows both simplex and discontinuous gapping under a single type assignment
2017-01-17T14:00:39ZValentín Fernández Gallart, José OriolMorrill, GlynIn a series of papers Kubota and Levine give an account of gapping and determiner gapping in terms of hybrid type logical grammar, including anomalous scopal interactions with auxiliaries and negative quantifiers. We make three observations: i) under the counterpart assumptions that Kubota and Levine make, the existent displacement type logical grammar account of gapping already accounts for the scopal interactions, ii) Kubota and Levine overgenerate determiner-verb order permutations in determiner gapping conjuncts whereas the immediate adaptation of their proposal to displacement type logical grammar does not do so, and iii) Kubota and Levine do not capture simplex gapping as a special case of complex gapping, but require distinct lexical entries for the two cases; we show how a generalisation of displacement type logical grammar allows both simplex and discontinuous gapping under a single type assignmenth-graphs: A new representation for tree decompositions of graphs
http://hdl.handle.net/2117/99483
h-graphs: A new representation for tree decompositions of graphs
Hidalgo Garcia, Marta; Joan Arinyo, Robert
In geometric constraint solving, well constrained geometric problems can be abstracted as Laman graphs. If the graph is tree decomposable, the constraint-based geometric problem can be solved by a Decomposition-Recombination planner based solver. In general decomposition and recombination steps can be completed only when other steps have already been completed. This fact naturally defines a hierarchy in the decomposition-recombination steps that traditional tree decomposition representations do not capture explicitly. In this work we introduce h-graphs, a new representation for decompositions of tree decomposable Laman graphs, which captures dependence relations between different tree decomposition steps. We show how h-graphs help in efficiently computing parameter ranges for which solution instances to well constrained, tree decomposable geometric constraint problems with one degree of freedom can actually be constructed.
2017-01-17T13:41:49ZHidalgo Garcia, MartaJoan Arinyo, RobertIn geometric constraint solving, well constrained geometric problems can be abstracted as Laman graphs. If the graph is tree decomposable, the constraint-based geometric problem can be solved by a Decomposition-Recombination planner based solver. In general decomposition and recombination steps can be completed only when other steps have already been completed. This fact naturally defines a hierarchy in the decomposition-recombination steps that traditional tree decomposition representations do not capture explicitly. In this work we introduce h-graphs, a new representation for decompositions of tree decomposable Laman graphs, which captures dependence relations between different tree decomposition steps. We show how h-graphs help in efficiently computing parameter ranges for which solution instances to well constrained, tree decomposable geometric constraint problems with one degree of freedom can actually be constructed.Firefighting as a Game
http://hdl.handle.net/2117/99479
Firefighting as a Game
Álvarez Faura, M. del Carme; Blesa Aguilera, Maria Josep; Molter, Hendrik
The Firefighter Problem was proposed in 1995 [16] as a deterministic discrete-time model for the spread (and containment) of a fire. Its applications reach from real fires to the spreading of deseases and the containment of floods. Furthermore, it can be used to model the spread of computer viruses or viral marketing in communication networks. In this work, we study the problem from a game-theorical perspective. Such a context seems very appropriate when applied to large networks, where entities may act and make decisions based on their own interests, without global coordination. We model the Firefighter Problem as a strategic game where there is one player for each time step who decides where to place the firefighters. We show that the Price of Anarchy is linear in the general case, but at most 2 for trees. We prove that the quality of the equilibria improves when allowing coalitional cooperation among players. In general, we have that the Price of Anarchy is in O( n / k ) where k is the coalition size. Furthermore, we show that there are topologies which have a constant Price of Anarchy even when constant sized coalitions are considered.
2017-01-17T13:25:59ZÁlvarez Faura, M. del CarmeBlesa Aguilera, Maria JosepMolter, HendrikThe Firefighter Problem was proposed in 1995 [16] as a deterministic discrete-time model for the spread (and containment) of a fire. Its applications reach from real fires to the spreading of deseases and the containment of floods. Furthermore, it can be used to model the spread of computer viruses or viral marketing in communication networks. In this work, we study the problem from a game-theorical perspective. Such a context seems very appropriate when applied to large networks, where entities may act and make decisions based on their own interests, without global coordination. We model the Firefighter Problem as a strategic game where there is one player for each time step who decides where to place the firefighters. We show that the Price of Anarchy is linear in the general case, but at most 2 for trees. We prove that the quality of the equilibria improves when allowing coalitional cooperation among players. In general, we have that the Price of Anarchy is in O( n / k ) where k is the coalition size. Furthermore, we show that there are topologies which have a constant Price of Anarchy even when constant sized coalitions are considered.