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  • Support service for reciprocal computational resource sharing in wireless community networks

     Buyuksahin, Umit C.; Khan, Muhammad Amin; Freitag, Felix
    IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks
    Presentation's date: 2013-06
    Presentation of work at congresses

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    In community networks, individuals and local organizations from a geographic area team up to create and run a community-owned IP network to satisfy the community's demand for ICT, such as facilitating Internet access and providing services of local interest. Most current community networks use wireless links for the node interconnection, applying off-the-shelf wireless equipment. While IP connectivity over the shared network infrastructure is successfully achieved, the deployment of applications in community networks is surprisingly low. To address the solution of this problem, we propose in this paper a service to incentivize the contribution of computing and storage as cloud resources to community networks, in order to stimulate the deployment of services and applications. Our final goal is the vision that in the long term, the users of community networks will not need to consume applications from the Internet, but find them within the wireless community network.

  • Effort-based incentives for resource sharing in collaborative volunteer applications

     Vega D'Aurelio, Davide; Meseguer Pallares, Roque; Freitag, Felix; Ochoa, Sergio
    International Conference on Computer Supported Cooperative Work in Design
    Presentation's date: 2013-06-27
    Presentation of work at congresses

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    Collaborative and volunteer applications need to implement incentive mechanisms to regulate resource sharing and encourage network nodes to contribute for reaching a certain goal. Typically, these incentive mechanisms assign resources to network node requests, based on the total amount of resources contributed by the requesting participant. This approach assumes that participants contributing more should also get back more resources from the collaborative environment. This assumption turns the system unfair to those participants with scarce resources, because they have just few resources to share. This paper proposes the use of an incentive strategy based on the contribution percentage of each node; i.e. an effort-based approach. This proposal is evaluated and compared to contribution-based strategies. The obtained results show that the proposed effort-based approach not only benefits participants that have scarce resources, but also it is able to satisfy the requests of the powerful nodes.

    Collaborative and volunteer applications need to implement incentive mechanisms to regulate resource sharing and encourage network nodes to contribute for reaching a certain goal. Typically, these incentive mechanisms assign resources to network node requests, based on the total amount of resources contributed by the requesting participant. This approach assumes that participants contributing more should also get back more resources from the collaborative environment. This assumption turns the system unfair to those participants with scarce resources, because they have just few resources to share. This paper proposes the use of an incentive strategy based on the contribution percentage of each node; i.e. an effort-based approach. This proposal is evaluated and compared to contribution-based strategies. The obtained results show that the proposed effort-based approach not only benefits participants that have scarce resources, but also it is able to satisfy the requests of the powerful nodes.

  • Incentivos basados en el esfuerzo para compartir recursos en aplicaciones colaborativas

     Vega D'Aurelio, Davide; Meseguer Pallares, Roque; Freitag, Felix; Navarro Moldes, Leandro
    Jornadas de Concurrencia y Sistemas Distribuidos
    Presentation's date: 2013-06-20
    Presentation of work at congresses

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    Las aplicaciones colaborativas voluntarias necesitan implementar mecanismos de incentivos para regular la compartición de los recursos y fomentar la contribución de los nodos de la red. Por lo general, estos mecanismos de incentivos asignan recursos a los nodos bajo petición, y se basan en la cantidad total de los recursos aportados por el solicitante. Este enfoque asume que los participantes que más contribuyen deben también obtener más recursos del entorno colaborativo. Esta suposición hace el sistema injusto para los participantes con escasos recursos ya que tienen problemas para compartir debido a sus pocos recursos. En este trabajo proponemos el uso de una estrategia de incentivos basada en la relación entre la contribución y los recursos de cada nodo, es decir, un enfoque basado en el esfuerzo. Evaluamos y comparamos esta propuesta con las estrategias basadas en la contribución. Los resultados obtenidos muestran que el enfoque propuesto basado en el esfuerzo no sólo beneficia a los participantes que cuentan con escasos recursos, sino también es capaz de satisfacer las peticiones de los nodos con mayores recursos.

  • A summary of virtualization techniques

     Rodríguez Haro, Fernando; Freitag, Felix; Navarro Moldes, Leandro; Hernández Sánchez, Efraín; Farías Mendoza, Nicandro; Guerrero Ibañez, Juan Antonio; González Potes, Apolinar
    Iberoamerican Conference on Electronics Engineering and Computer Science
    Presentation of work at congresses

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  • Towards incentive-based resource assignment and regulation in clouds for community networks

     Khan, Muhammad Amin; Buyuksahin, Umit C.; Freitag, Felix
    International Conference on Economics of Grids, Clouds, Systems and Services
    Presentation's date: 2013-09
    Presentation of work at congresses

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    Community networks are built with off-the-shelf communication equipment aiming to satisfy a community's demand for Internet access and services. These networks are a real world example of a collective that shares ICT resources. But while these community networks successfully achieve the IP connectivity over the shared network infrastructure, the deployment of applications inside of community networks is surprisingly low. Given that community networks are driven by volunteers, we believe that bringing in incentive-based mechanisms for service and application deployments in community networks will help in unlocking its true potential. We investigate in this paper such mechanisms to steer user contributions, in order to provide cloud services from within community networks. From the analysis of the community network's topology, we derive two scenarios of community clouds, the local cloud and the federated cloud. We develop an architecture tailored to community networks which integrates the incentive mechanism we propose. In simulations of large scale community cloud scenarios we study the behaviour of the incentive mechanism in different configurations, where slices of homogeneous virtual machine instances are shared. Our simulation results allow us to understand better how to configure such an incentive mechanism in a future prototype of a real community cloud system, which ultimately should lead to realisation of clouds in community networks.

  • Sharing hardware resources in heterogeneous computer-supported collaboration scenarios

     Vega D'Aurelio, Davide; Meseguer Pallares, Roque; Ochoa, Sergio; Pino, José; Freitag, Felix; Medina, Esunly; Royo Valles, Maria Dolores
    Integrated computer-aided engineering
    Date of publication: 2013-01
    Journal article

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  • Premi a la Diversitat Cultural i Identitat, Diversitat Lingüística i Contingut Local

     Casanellas, Felix; Navarro Moldes, Leandro; Freitag, Felix
    Award or recognition

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  • A Community networking Cloud in a box

     Freitag, Felix
    Participation in a competitive project

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  • A QoS App-SLO manager for virtualized infrastructure

     Rodríguez Haro, Fernando; Freitag, Felix; Navarro Moldes, Leandro
    Polibits: research journal on computer science and computer engineering with applications
    Date of publication: 2012
    Journal article

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  • A summary of virtualization techniques

     Rodríguez Haro, Fernando; Freitag, Felix; Navarro Moldes, Leandro; Hernández Sánchez, Efraín; Farías Mendoza, Nicandro; Guerrero Ibañez, Juan Antonio; González Potes, Apolinar
    Procedia Technology
    Date of publication: 2012
    Journal article

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  • Estimación automática de grupos en entornos de aprendizaje cooperativo con aplicaciones sensibles al contexto  Open access

     Meseguer Pallares, Roque
    Defense's date: 2012-03-02
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    In collaborative learning scenarios, the use of computers and communication networks to facilitate collaboration is becoming popular, the Computer-Supported Collaborative Learning (CSCL). In face-to-face CSCL scenarios, participants are grouped for learning activities. The location information of the participants, very useful for computational support, may involve additional configuration work for students or teachers themselves. Mobile devices that facilitate this cooperation have evolved into ubiquitous computing. Sensing devices can capture context information that allows automate the detection of the location of users and objects involved in the learning scenario and use this contextual information to improve the support offered by computers. This thesis deals in detail the problem of computational support to the detection and management of learning groups in faceto-face CSCL environments. Our research has focused on the proposal of a system that automates the management of groups in these scenarios collecting and processing contextual information from sensors. To do this we have proposed a context model for this use and we have identified what information is most relevant to this domain application. This process of modeling and identification have been theoretical ---from conceptual frameworks that have allowed us to define a model of context--- and experimental ---from assessing the quality, reliability and sensitivity of contextual information in realistic environments---. Then we have verified how this contextual information fits the contextual model. Contextual information can pass through several stages before being used. First, the contextual information collected by the sensors could be conditioned and filtered to treat quality and uncertainty. Then it is supplied to an intelligent system that learns behavior patterns of groups and students. This intelligent system requires two different operating processes: training and estimation. We have proposed specific training and assessment processes for prediction and management of groups. The output also could be conditioned as it was done with the input. Finally, we used traces of contextual information in real scenarios ---real students doing group learning activities--- to validate the system. In this validation we have taken into account both the effectiveness and their impact on the activity of students and groups. From this impact assessment we have identified patterns in the contextual information and in the behavior that have allowed us to design a system of quality, error and uncertainty management in the group estimation and a filtering system and interpolation of contextual information ambiguous, missing or erroneous, and filtering and interpolation system of ambiguous, missing or erroneous contextual information. Our thesis is that to provide computational support to the detection and management of learning groups in face-to-face CSCL environments we need three basic functionalities: 1) the collection and filtering of changes in contextual information in realtime for each student and adjust them in the context model, 2) the transformation of this contextual information and thier historical to group membership by an intelligent algorithm and 3) the quality management of group estimations to minimize the impact on activity of students because of the uncertainty of these estimations.

    En escenaris d’aprenentatge col·laboratiu, s'ha introduït l’ús d’ordinadors i xarxes de comunicacions per facilitar aquesta col·laboració, l’anomenat “Computer-Supported Collaborative Learning” (CSCL). En escenaris CSCL presencials els participants s’agrupen per realitzar activitats d’aprenentatge. Aquesta informació sobre la disposició dels participants, de gran utilitat per al suport computacional, pot suposar un treball addicional de configuració per als propis estudiants o els professors. Els dispositius electrònics per facilitar aquesta cooperació han evolucionat fins la computació ubiqua, en la que dispositius sensors poden captar informació que permet a las aplicacions informàtiques automatitzar la detecció de la ubicació dels usuaris i objectes participants en l’escenari d’aprenentatge i usar aquesta informació contextual per millorar el suport ofert per els dispositius.Aquesta tesis tracta amb detall el problema del suport computacional a la detecció i gestió de grups d’aprenentatge en entorns CSCL presencials. La nostra investigació s’ha centrat en proposar un sistema que a partir de la recollida d’informació contextual proporcionada per sensors, automatitzi la gestió de grups en aquests escenaris CSCL presencials.Per açò hem proposat un modelo de context per aquest ús i hem identificat quina informació es mes rellevant per aquest proposit. Aquest modelat i identificació han estat tant teòrics ---a partir de marcs conceptuals que ens han permès definir un modelo de context--- com experimentals ---a partir de l’avaluació de la qualitat, fiabilitat i sensibilitat de la informació contextual en entorns realistes---. Finalment hem verificat cóm aquest informació contextual del nostre escenari s’adapta a aquest model.La informació contextual passa per varies fases per poder ser usada. Primer aquesta informació percebuda per els sensors es pot condicionar i filtrar per tractar la seva qualitat i incertesa. A continuació es subministra a un sistema intel·ligent que aprèn els patrons de funcionament dels grups i estudiants. Aquest sistema intel·ligent requereix dos processos diferents de funcionament: l’entrenament i l’estimació. Nosaltres hem proposat uns processos d’entrenament i estimació específics per la predicció i gestió de grups. També es pot tornar a condicionar la sortida igual que s’ha fet amb l’entrada.Finalment, per la validació del sistema hem utilitzat traces d’informació contextual d’escenaris reals ---amb estudiants reals realitzant activitats d’aprenentatge en grup---. En aquesta validació hem tingut present tant l’eficàcia del sistema como el seu impacte en l’activitat dels estudiants i grups. A partir d’aquest impacte hem identificat patrons en la informació contextual y en el comportament que ens ha permès introduir un sistema de gestió de la qualitat, errors i incertesa en la estimació, així com un sistema de filtratge i interpolació de la informació contextual ambigua, inexistent o errònia.La nostra tesis es que per proporcionar suport computacional a la detecció i estimació de grups de treball en activitats d'aprenentatge presencial en entorns CSCL són necessàries tres funcionalitats bàsiques: 1) la recol·lecció i filtrat en temps real dels canvis de la informació contextual de cada estudiant i recollir-los en el model contextual, 2) la transformació d'aquesta informació contextual el seu històric a informació contextual de grup per part d'un algoritme intel·ligente i 3) la gestió de la qualitat de les estimacions de grup per minimitzar l'impacte en l'atenció dels estudiants degut a la incertesa d'aquestes estimacions.

    En escenarios de aprendizaje colaborativo, se ha introducido el uso de ordenadores y redes de comunicación para facilitar esta colaboración, el llamado “Computer-Supported Collaborative Learning” (CSCL). En escenarios CSCL presenciales los participantes se agrupan para realizar actividades de aprendizaje. La información sobre la disposición de los participantes, de gran utilidad para dar soporte computacional, puede suponer un trabajo adicional de configuración para los propios estudiantes o los profesores. Los dispositivos electrónicos para facilitar esta cooperación han evolucionado hasta la computación ubicua, en que dispositivos sensores pueden captar información que permite a las aplicaciones informáticas automatizar la detección de la ubicación de los usuarios y objetos participantes en el escenario de aprendizaje y usar esa información contextual para mejorar el soporte ofrecido.Este trabajo trata con detalle el problema del soporte computacional a la detección y gestión de grupos de aprendizaje en entornos CSCL presenciales. Nuestra investigación se ha centrado en proponer un sistema que a partir de la recogida de información contextual proveniente de sensores, automatice la gestión de grupos en estos escenarios CSCL presenciales.Para ello hemos propuesto un modelo de contexto para este uso y hemos identificado qué información es más relevante para este propósito. Este modelado e identificación han sido tanto teóricos ---a partir de marcos conceptuales que nos han permitido definir un modelo de contexto--- como experimentales ---a partir de la evaluación de la calidad, fiabilidad y sensibilidad de la información contextual en entornos realistas---. Finalmente hemos verificado cómo esta información contextual de nuestro escenario se adapta a este modelo.La información contextual pasa por varias fases para ser usada. Primero esta información percibida por los sensores se puede acondicionar y filtrar para tratar su calidad e incertidumbre. A continuación se suministra a un sistema inteligente que aprende los patrones de funcionamiento de los grupos y estudiantes. Este sistema inteligente requiere dos procesos diferentes de funcionamiento: el entrenamiento y la estimación. Nosotros hemos propuesto unos procesos de entrenamiento y estimación específicos para la predicción y gestión de grupos. También se puede volver a acondicionar la salida como ya se ha hecho con la entrada.Finalmente, para la validación del sistema hemos utilizado trazas de información contextual de escenarios reales ---con estudiantes reales realizando actividades de aprendizaje en grupo---. En esta validación hemos tenido en cuenta tanto la eficacia del sistema como su impacto en la actividad de los estudiantes y grupos. A partir de este impacto hemos identificado ciertos patrones en la información contextual y en el comportamiento que nos ha permitido introducir un sistema de gestión de la calidad, errores e incertidumbre en la estimación así como un sistema de filtrado e interpolación de la información contextual ambigua, inexistente o errónea.Nuestra tesis es que para proporcionar soporte computacional a la detección y estimación de grupos de trabajo en actividades de aprendizaje presenciales en entornos CSCL son necesarias tres funcionalidades básicas: 1) la recolección y filtrado en tiempo real de los cambios de la información contextual de cada estudiante y recogerlos en el modelo contextual, 2) la transformación de esta información contextual y su histórico a información contextual de grupo por parte de un algoritmo inteligente y 3) la gestión de la calidad de las estimaciones de grupo para minimizar el impacto en la atención de los estudiantes debido a la incertidumbre de estas estimaciones.

  • An Online Writer Recognition System Based On In-Air And On-Surface Trajectories  Open access

     Sesa Nogueras, Enric
    Defense's date: 2012-09-20
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    The main motivation of this dissertation is the exploration of the field of online text-dependent writer recognition, in order to provide evidence of the usefulness of short sequences of text to perform identification and verification, which are the two tasks involved in recognition. From this motivation stem its main goals and contributions: an exploration performed from a practical perspective, thus requiring the development of a recognition system, and the gathering of evidence concerning the discriminative power of in-air trajectories (the trajectories described while not exerting any pressure on the writing surface, when the hand moves in the air while transitioning from one stroke to the next), i.e. their ability to discriminate among writers. In-air and on-surface trajectories have been analyzed from the perspective of information theory and the results yielded by this analysis show that, except for pressure, they contain virtually equal amounts of information and are notably non-redundant. This suggests that in-air trajectories may have a considerable discriminative power and that they may help improve the overall recognition performance when combined with on-surface trajectories. An innovative writer recognition system that fulfils the abovementioned practical goal has been devised. It follows an allographic approach, that is, it does not take into account the global characteristics of the text but focuses on character and character-fragment shapes. Strokes are considered the structural units of handwriting and any piece of text is regarded as two separate sequences, one of pen-up and one of pen-down strokes. The system relies on a pair of catalogues of strokes, built in an unsupervised manner by means of self-organizing maps, which allow mapping sequences of strokes into sequences of integers. The latter sequences, much simpler than the original ones, can be effectively compared by means of dynamic time warping, which takes advantage of the neighbouring properties exhibited by self-organizing maps. Measures obtained from each sequence can be combined in a later step. The recognition system has been experimentally tested using 16 uppercase words from the BiosecurID database, which contains 4 executions of each word donated by 400 writers. The experimental results obtained clearly sustain the claim that online words have a notable recognition potential and show the suitability of the allographic approach to perform writer recognition in the online text-dependent context. Regarding identification, the system compares positively to other word-based identification schemas. As for verification, the accuracy levels attained do not lie much below the accuracies reported for today¿s state-of-the-art signature verification methods. Furthermore, the results obtained from in-air trajectories have substantiated what the information analysis had already suggested: their considerable recognition power and their notable non-redundancy with respect to on-surface trajectories. Finally, a new method to generate synthetic samples of online words from real ones has been proposed. This method is based on the recognition system previously described, takes advantage of its main characteristics and can be seamlessly integrated into it. Synthetic samples are used to enlarge the enrolment sets, which has the effect of substantially improving the recognition accuracy of the system.

    La principal motivació d’aquesta dissertació és la investigació en el camp del reconeixement d’escriptors en la modalitat online depenent del text, amb intenció de proporcionar evidències que avalin la utilitat de les seqüències curtes per a la identificació i la verificació, que són les dues tasques compreses en el reconeixement. D’aquesta motivació se’n deriven els seus objectius més rellevants: una exploració feta des d’una perspectiva pràctica que requereix, doncs, el desenvolupament d’un sistema de reconeixement; i la recerca d’evidència relacionada amb la potència discriminant de les trajectòries en l’aire (aquelles que són executades sense que l’estri d’escriptura exerceixi pressió sobre la superfície, en les transicions entre traços), això és, la seva capacitat per a reconèixer escriptors. Les trajectòries en l’aire i sobre la superfície han estat analitzades des de la perspectiva de la teoria de la informació. Els resultats obtinguts d’aquesta anàlisi mostren que, llevat de la pressió, ambdós tipus de trajectòries contenen quantitats d’informació pràcticament idèntiques, amb un nivell notable de no redundància. Això suggereix que les trajectòries en l’aire potser posseeixen una potència discriminant considerable i que la capacitat global de reconeixement pot millorar si es combinen amb les trajectòries sobre la superfície. S’ha desenvolupat un sistema de reconeixement innovador que representa l’assoliment de l’objectiu pràctic. Aquest sistema està basat en una aproximació al•logràfica, això és, no té en compte les característiques globals del text sinó que està focalitzat en les formes dels caràcters i dels seus fragments. Els traços són considerats la unitat estructural bàsica de l’escriptura i qualsevol fragment de text és entès com un parell de seqüències separades, una de traços en superfície i una de traços elevats. El sistema treballa en base a un parell de catàlegs de traços, construïts de manera no supervisada amb l’ajut de mapes autoorganitzats, que li permeten transformar les seqüències de traços en seqüències de números enters. Aquestes darreres seqüències, molt més simples que no pas les originals, poden ser comparades, de manera efectiva, mitjançant el dynamic time warping (alineament temporal dinàmic) el qual treu profit de les propietats de veïnatge característiques dels mapes autoorganitzats. Les mesures que s’obtenen de cada seqüència poden ser combinades en un pas posterior. El sistema de reconeixement ha estat provat experimentalment fent ús de les 16 paraules en majúscules de la base de dades BiosecurID, la qual en conté 4 realitzacions de cadascuna donades per 400 persones. Els resultats experimentals que s’han obtingut recolzen clarament l’afirmació que les paraules online presenten una potència discriminant notable i avalen l’adequació de l’aproximació al•logràfica per a dur a terme reconeixement d’escriptors en el context online depenent del text. Quant a la identificació, el sistema es compara favorablement amb altres mètodes basats en paraules. I, pel que fa a la verificació, els nivells de precisió obtinguts no es troben gaire lluny dels nivells assolits pels mètodes de verificació de signatura representatius de l’estat de l’art actual. És més, els resultats que s’obtenen de les trajectòries en l’aire han corroborat allò que havia estat suggerit per l’anàlisi de la informació: la seva considerable potència discriminant i la seva substancial manca de redundància respecte de les trajectòries sobre la superfície. Finalment, s’ha proposat un nou sistema de generació de mostres sintètiques de paraules online. Aquest mètode està basat en el sistema de reconeixement abans descrit, n’aprofita les característiques principals i s’hi pot integrar amb facilitat. Les mostres sintètiques s’utilitzen per engrandir els conjunts d’inscripció (enrolment sets), la qual cosa té com a efecte una millora substancial de la precisió del sistema.

  • Network-aware summarisation for resource discovery in P2P-content networks

     Brunner, René; Caminero, A.C.; Rana, Omer; Freitag, Felix; Navarro Moldes, Leandro
    Future generation computer systems
    Date of publication: 2012
    Journal article

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  • Self-adaptive approximate queries for large-scale information aggregation

     Brunner, René; Freitag, Felix; Navarro Moldes, Leandro; Rana, Omer
    International journal of web and grid services
    Date of publication: 2012-09
    Journal article

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    Self-adaptation enables distributed software to modify its behaviour based on changes in the operating environment. In large-scale information systems for cloud computing that use hierarchical data aggregation, self-adaption may be used to respond to an approximate query, thereby reducing use of network bandwidth and retrieval time. We present a novel algorithm that uses an Analytic Hierarchical Process (AHP) in order to apply self-adaption to approximate queries based on network-awareness. The AHP-based algorithm provides a trade-off among network usage, retrieval time and the accuracy of the retrieved results. Simulations show that the number of needed messages reduces with AHP to a constant upper bound. The retrieval time reduces to a constant factor under an increasing number of nodes. Our results demonstrate that the algorithm is able to provide responses with the required accuracy, primarily by adapting the depth of the query based on the number of messages and the network conditions.

  • Characterizing the effects of sharing hardware resources in mobile collaboration scenarios

     Vega D'Aurelio, Davide; Medina Medina, Esunly; Meseguer Pallares, Roque; Royo Valles, Maria Dolores; Freitag, Felix; Ochoa, Sergio; Pino, José
    International Conference on Computer Supported Cooperative Work in Design
    Presentation's date: 2011
    Presentation of work at congresses

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  • Self-regulated trade-off among timeliness, messages and accuracy for approximate queries in large-scale information aggregation

     Brunner, René; Freitag, Felix; Navarro Moldes, Leandro
    International Conference on Network-Based Information Systems
    Presentation's date: 2011-09-07
    Presentation of work at congresses

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    In data management for large-scale applications such as Peer-to-Peer networks, and Grid and Cloud Computing arise challenges in regard to the decentralization of the application and in regard to an increasing number of failures. A consequence of these conditions is an increasing retrieval time, inaccurate results and higher network consumption. A solution to restrain an increasing retrieval time and an increasing number of messages is the introduction of approximate queries. The introduction of approximate queries limits the querying of all nodes of a network to a subset of nodes in the cost of the results' accuracy. Thus, a conflict to provide a large-scalability lies in guaranteeing accurate data, in the provision of fast results and in a low consumption of network bandwidth. Therefore, we propose an information aggregation that is based on an analytic hierarchical process (AHP) to find a trade-off among the unpredictable factors of time, messages and accuracy. After a user defines the preferences for the retrieval process, the AHP-based algorithm makes autonomous decisions on each node. The algorithm decides autonomously about pruning the approximate queries to reach an optimal trade-off from a global perspective. Applying the self-regulated pruning of the approximate queries allows reducing the messages from an exponential in crease to a constant factor. At the same time, the retrieval time is reduced from a linear increase to a constant factor in regard to an increasing number of nodes. At the same time of reducing the retrieval time and network bandwidth, the AHP-based self-regulation guarantees certain level of accuracy

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    Diseño e implementación de un simulador para explorar la cooperación en entornos distribuidos  Open access

     Vega D'Aurelio, Davide; Meseguer Pallares, Roque; Freitag, Felix
    Jornadas de Concurrencia y Sistemas Distribuidos
    Presentation's date: 2011-06
    Presentation of work at congresses

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    Los avances tecnológicos en los sistemas de comunicación y computación móviles están impulsando la emergencia de sistemas colaborativos distribuidos. No obstante, la participación de los usuarios se ve frenada por los escasos recursos disponibles en los dispositivos móviles actuales. En este artículo se presenta un simulador de redes colaborativas descentralizadas que permite estudiar cómo la topología de la red y las estrategias de los diferentes participantes pueden incentivar y mejorar su participación activa {colaboración{ en este tipo de escenarios. Los resultados obtenidos en las simulaciones realizadas sobre redes de overlay, nos han permitido realizar observaciones importantes en cuánto a cómo distribuir los recursos en las redes con dispositivos heterogéneos, qué tipo de estrategias de colaboración y colocación de nodos o qué topologías pueden incentivar la participación activa. Por ello, consideramos el simulador una buena herramienta para analizar este tipo de escenarios desde un punto de vista empírico.

  • A node placement heuristic to encourage resource sharing in mobile computing

     Vega D'Aurelio, Davide; Medina Medina, Esunly; Meseguer Pallares, Roque; Royo Valles, Maria Dolores; Freitag, Felix
    International Conference on Computational Science and Its Applications
    Presentation's date: 2011-06-23
    Presentation of work at congresses

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  • Trade-off Among Timeliness, Messages and Accuracy For Large-Scale Information Management  Open access

     Brunner, René
    Defense's date: 2011-11-18
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    The increasing amount of data and the number of nodes in large-scale environments require new techniques for information management. Examples of such environments are the decentralized infrastructures of Computational Grid and Computational Cloud applications. These large-scale applications need different kinds of aggregated information such as resource monitoring, resource discovery or economic information. The challenge of providing timely and accurate information in large scale environments arise from the distribution of the information. Reasons for delays in distributed information system are a long information transmission time due to the distribution, churn and failures. A problem of large applications such as peer-to-peer (P2P) systems is the increasing retrieval time of the information due to the decentralization of the data and the failure proneness. However, many applications need a timely information provision. Another problem is an increasing network consumption when the application scales to millions of users and data. Using approximation techniques allows reducing the retrieval time and the network consumption. However, the usage of approximation techniques decreases the accuracy of the results. Thus, the remaining problem is to offer a trade-off in order to solve the conflicting requirements of fast information retrieval, accurate results and low messaging cost. Our goal is to reach a self-adaptive decision mechanism to offer a trade-off among the retrieval time, the network consumption and the accuracy of the result. Self-adaption enables distributed software to modify its behavior based on changes in the operating environment. In large-scale information systems that use hierarchical data aggregation, we apply self-adaptation to control the approximation used for the information retrieval and reduces the network consumption and the retrieval time. The hypothesis of the thesis is that approximation techniquescan reduce the retrieval time and the network consumption while guaranteeing an accuracy of the results, while considering user’s defined priorities. First, this presented research addresses the problem of a trade-off among a timely information retrieval, accurate results and low messaging cost by proposing a summarization algorithm for resource discovery in P2P-content networks. After identifying how summarization can improve the discovery process, we propose an algorithm which uses a precision-recall metric to compare the accuracy and to offer a user-driven trade-off. Second, we propose an algorithm that applies a self-adaptive decision making on each node. The decision is about the pruning of the query and returning the result instead of continuing the query. The pruning reduces the retrieval time and the network consumption at the cost of a lower accuracy in contrast to continuing the query. The algorithm uses an analytic hierarchy process to assess the user’s priorities and to propose a trade-off in order to satisfy the accuracy requirements with a low message cost and a short delay. A quantitative analysis evaluates our presented algorithms with a simulator, which is fed with real data of a network topology and the nodes’ attributes. The usage of a simulator instead of the prototype allows the evaluation in a large scale of several thousands of nodes. The algorithm for content summarization is evaluated with half a million of resources and with different query types. The selfadaptive algorithm is evaluated with a simulator of several thousands of nodes that are created from real data. A qualitative analysis addresses the integration of the simulator’s components in existing market frameworks for Computational Grid and Cloud applications. The proposed content summarization algorithm reduces the information retrieval time from a logarithmic increase to a constant factor. Furthermore, the message size is reduced significantly by applying the summarization technique. For the user, a precision-recall metric allows defining the relation between the retrieval time and the accuracy. The self-adaptive algorithm reduces the number of messages needed from an exponential increase to a constant factor. At the same time, the retrieval time is reduced to a constant factor under an increasing number of nodes. Finally, the algorithm delivers the data with the required accuracy adjusting the depth of the query according to the network conditions.

    La gestió de la informació exigeix noves tècniques que tractin amb la creixent quantitat de dades i nodes en entorns a gran escala. Alguns exemples d’aquests entorns són les infraestructures descentralitzades de Computacional Grid i Cloud. Les aplicacions a gran escala necessiten diferents classes d’informació agregada com monitorització de recursos i informació econòmica. El desafiament de proporcionar una provisió ràpida i acurada d’informació en ambients de grans escala sorgeix de la distribució de la informació. Una raó és que el sistema d’informació ha de tractar amb l’adaptabilitat i fracassos d’aquests ambients. Un problema amb aplicacions molt grans com en sistemes peer-to-peer (P2P) és el creixent temps de recuperació de l’informació a causa de la descentralització de les dades i la facilitat al fracàs. No obstant això, moltes aplicacions necessiten una provisió d’informació puntual. A més, alguns usuaris i aplicacions accepten inexactituds dels resultats si la informació es reparteix a temps. A més i més, el consum de xarxa creixent fa que sorgeixi un altre problema per l’escalabilitat del sistema. La utilització de tècniques d’aproximació permet reduir el temps de recuperació i el consum de xarxa. No obstant això, l’ús de tècniques d’aproximació disminueix la precisió dels resultats. Així, el problema restant és oferir un compromís per resoldre els requisits en conflicte d’extracció de la informació ràpida, resultats acurats i cost d’enviament baix. El nostre objectiu és obtenir un mecanisme de decisió completament autoadaptatiu per tal d’oferir el compromís entre temps de recuperació, consum de xarxa i precisió del resultat. Autoadaptacío permet al programari distribuït modificar el seu comportament en funció dels canvis a l’entorn d’operació. En sistemes d’informació de gran escala que utilitzen agregació de dades jeràrquica, l’auto-adaptació permet controlar l’aproximació utilitzada per a l’extracció de la informació i redueixen el consum de xarxa i el temps de recuperació. La hipòtesi principal d’aquesta tesi és que els tècniques d’aproximació permeten reduir el temps de recuperació i el consum de xarxa mentre es garanteix una precisió adequada definida per l’usari. La recerca que es presenta, introdueix un algoritme de sumarització de continguts per a la descoberta de recursos a xarxes de contingut P2P. Després d’identificar com sumarització pot millorar el procés de descoberta, proposem una mètrica que s’utilitza per comparar la precisió i oferir un compromís definit per l’usuari. Després, introduïm un algoritme nou que aplica l’auto-adaptació a un ordre per satisfer els requisits de precisió amb un cost de missatge baix i un retard curt. Basat en les prioritats d’usuari, l’algoritme troba automàticament un compromís. L’anàlisi quantitativa avalua els algoritmes presentats amb un simulador per permetre l’evacuació d’uns quants milers de nodes. El simulador s’alimenta amb dades d’una topologia de xarxa i uns atributs dels nodes reals. L’algoritme de sumarització de contingut s’avalua amb mig milió de recursos i amb diferents tipus de sol·licituds. L’anàlisi qualitativa avalua la integració del components del simulador en estructures de mercat existents per a aplicacions de Computacional Grid i Cloud. Així, la funcionalitat implementada del simulador (com el procés d’agregació i la query language) és comprovada per la integració de prototips. L’algoritme de sumarització de contingut proposat redueix el temps d’extracció de l’informació d’un augment logarítmic a un factor constant. A més, també permet que la mida del missatge es redueix significativament. Per a l’usuari, una precision-recall mètric permet definir la relació entre el nivell de precisió i el temps d’extracció de la informació. Alhora, el temps de recuperació es redueix a un factor constant sota un nombre creixent de nodes. Finalment, l’algoritme reparteix les dades amb la precisió exigida i ajusta la profunditat de la sol·licitud segons les condicions de xarxa. Els algoritmes introduïts són prometedors per ser utilitzats per l’agregació d’informació en nous sistemes de gestió de la informació de gran escala en el futur.

  • A MIDDLEWARE FRAMEWORK FOR SELF-ADAPTIVE LARGE SCALE DISTRIBUTED SERVICES  Open access

     Chacin Martinez, Pablo Jesus
    Defense's date: 2011-07-21
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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    Modern service-oriented applications demand the ability to adapt to changing conditions and unexpected situations while maintaining a required QoS. Existing self-adaptation approaches seem inadequate to address this challenge because many of their assumptions are not met on the large-scale, highly dynamic infrastructures where these applications are generally deployed on. The main motivation of our research is to devise principles that guide the construction of large scale self-adaptive distributed services. We aim to provide sound modeling abstractions based on a clear conceptual background, and their realization as a middleware framework that supports the development of such services. Taking the inspiration from the concepts of decentralized markets in economics, we propose a solution based on three principles: emergent self-organization, utility driven behavior and model-less adaptation. Based on these principles, we designed Collectives, a middleware framework which provides a comprehensive solution for the diverse adaptation concerns that rise in the development of distributed systems. We tested the soundness and comprehensiveness of the Collectives framework by implementing eUDON, a middleware for self-adaptive web services, which we then evaluated extensively by means of a simulation model to analyze its adaptation capabilities in diverse settings. We found that eUDON exhibits the intended properties: it adapts to diverse conditions like peaks in the workload and massive failures, maintaining its QoS and using efficiently the available resources; it is highly scalable and robust; can be implemented on existing services in a non-intrusive way; and do not require any performance model of the services, their workload or the resources they use. We can conclude that our work proposes a solution for the requirements of self-adaptation in demanding usage scenarios without introducing additional complexity. In that sense, we believe we make a significant contribution towards the development of future generation service-oriented applications.

    Las Aplicaciones Orientadas a Servicios modernas demandan la capacidad de adaptarse a condiciones variables y situaciones inesperadas mientras mantienen un cierto nivel de servio esperado (QoS). Los enfoques de auto-adaptación existentes parecen no ser adacuados debido a sus supuestos no se cumplen en infrastructuras compartidas de gran escala. La principal motivación de nuestra investigación es inerir un conjunto de principios para guiar el desarrollo de servicios auto-adaptativos de gran escala. Nuesto objetivo es proveer abstraciones de modelaje apropiadas, basadas en un marco conceptual claro, y su implemetnacion en un middleware que soporte el desarrollo de estos servicios. Tomando como inspiración conceptos económicos de mercados decentralizados, hemos propuesto una solución basada en tres principios: auto-organización emergente, comportamiento guiado por la utilidad y adaptación sin modelos. Basados en estos principios diseñamos Collectives, un middleware que proveer una solución exhaustiva para los diversos aspectos de adaptación que surgen en el desarrollo de sistemas distribuidos. La adecuación y completitud de Collectives ha sido provada por medio de la implementación de eUDON, un middleware para servicios auto-adaptativos, el ha sido evaluado de manera exhaustiva por medio de un modelo de simulación, analizando sus propiedades de adaptación en diversos escenarios de uso. Hemos encontrado que eUDON exhibe las propiedades esperadas: se adapta a diversas condiciones como picos en la carga de trabajo o fallos masivos, mateniendo su calidad de servicio y haciendo un uso eficiente de los recusos disponibles. Es altamente escalable y robusto; puedeoo ser implementado en servicios existentes de manera no intrusiva; y no requiere la obtención de un modelo de desempeño para los servicios. Podemos concluir que nuestro trabajo nos ha permitido desarrollar una solucion que aborda los requerimientos de auto-adaptacion en escenarios de uso exigentes sin introducir complejidad adicional. En este sentido, consideramos que nuestra propuesta hace una contribución significativa hacia el desarrollo de la futura generación de aplicaciones orientadas a servicios.

  • SISTEMAS DISTRIBUIDOS AUTO-ADAPTABLES PARA LA INTERNET DEL FUTURO

     Chacin Martinez, Pablo Jesus; Royo Valles, Maria Dolores; Freitag, Felix; Meseguer Pallares, Roque; Reyes Muñoz, M. Angélica; Gallardo Gomez, Antonia; Vega D'Aurelio, Davide; Brunner, René; León Gutiérrez, Xavier; Medina Medina, Esunly; Lopez Berga, Ester; Navarro Moldes, Leandro
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  • Community Networks Testbed for the Future Internet

     Freitag, Felix; León Gutiérrez, Xavier; Meseguer Pallares, Roque; Lopez Berga, Ester; Vega D'Aurelio, Davide; Cerdà Alabern, Llorenç; Navarro Moldes, Leandro
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  • Toward QoS provision for virtualized resources in grids

     Rodríguez Haro, Fernando; Freitag, Felix; Navarro Moldes, Leandro
    Date of publication: 2010-03-10
    Book chapter

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    Virtualization solutions have recently gained considerable attention for supporting the consolidation of application servers into one physical machine. In a vanilla Xen implementation the scheduler shares equally all of the available physical CPU resources among the contending VMs. However, when the application that runs in the virtual machine space changes dynamically its resource requirements, a different solution is needed. Furthermore, if the resource usage is associated with service-level agreements, a predefined equal share of the processor power is not sufficient for the VMs. In this chapter, we present an approach to manage the QoS of virtualized resources in Grids. Our solution adjusts the resources needed by each VM according to an agreed QoS. We achieve this by a local resource manager (LRM), which we implemented as a prototype and deployed on Xen-virtualized machines. By means of experiments we show that the implemented management component can meet the service-level objectives (SLOs) by dynamically adjusting virtualized resources according to demand.

  • Enhancing virtual environments with QoS aware resource management

     Rodriguez-Haro, F; Freitag, Felix; Navarro Moldes, Leandro
    Annales des télecommunications. Annals of telecommunications
    Date of publication: 2009-06
    Journal article

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  • Autonomous Management in VM-based Resource Providers.

     Rodríguez Haro, Fernando
    Defense's date: 2009-07-15
    Department of Computer Architecture, Universitat Politècnica de Catalunya
    Theses

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  • Fostering efficiency of computational resource allocation - Integrating information services into markets

     Borissov, Nikolai; Brunner, René; Neumann, Dirk; Freitag, Felix; Navarro Moldes, Leandro; Weinhardt, Christof
    European Conference on Information Systems
    Presentation's date: 2009-06
    Presentation of work at congresses

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  • IE09.Conferencia internacional: Intelligent Environments 2009 (IE09, quinta edición)

     Royo Valles, Maria Dolores; Freitag, Felix; Reyes Muñoz, M. Angélica; Meseguer Pallares, Roque; Navarro Moldes, Leandro
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  • Regulation of resource allocation for experimental distributed systems

     Freitag, Felix; Navarro Moldes, Leandro
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  • Access to the full text
    On network flow management in virtualized environments  Open access

     Rodríguez Haro, Fernando; Freitag, Felix; Navarro Moldes, Leandro; Farías Mendoza, Nicandro; Guerrero Ibañez, Juan Antonio
    International Conference on Electrical Engineering, Computing Science and Automatic Control
    Presentation's date: 2009-11-10
    Presentation of work at congresses

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    Virtualization has enabled the use of virtual machine (VM) based resource providers to offer computing power as a service. However, one important feature is to have certainty about the planed or expected performance of the applications that run inside the VMs. Therefore, consolidating the work load of web-based applications, with time-varying resource requirements, should be done in an automated way. We present and evaluate a network flow management component for the admission control of HTTP connections. We study this component, in our local resource manager (LRM), by using two types of common Web-based applications. The preliminary results shows that we can meet the number of successful served requests and at the same time avoid the degradation in the application's response times.

  • A decentralized grid market infrastructure for service oriented grids

     Chao, I; Brunner, R; Freitag, Felix; Navarro Moldes, Leandro; Chacin Martinez, Pablo Jesus; Ardaiz, O; Joita, L; Rana, O F
    Wirtschaftsinformatik
    Date of publication: 2008-01
    Journal article

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  • Uncertainty Management for the Retrieval of Economic Information from Distributed Markets

     Brunner, Rene; Freitag, Felix; Navarro Moldes, Leandro
    Lecture notes in computer science
    Date of publication: 2008-10
    Journal article

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  • Improving the Introduction to a Collaborative Project-Based Course on Computer Network Applications

     Freitag, Felix; Navarro Moldes, Leandro; Marques Puig, Joan Manel
    Lecture notes in computer science
    Date of publication: 2008-06
    Journal article

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  • Uncertainty management for the retrieval of economic information for distributed markets

     Brunner, René; Freitag, Felix; Navarro Moldes, Leandro
    international conference on Scalable Uncertainty Management
    Presentation's date: 2008
    Presentation of work at congresses

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  • Core Services for Grid Markets

     Freitag, Felix
    From Grids to Service and Pervasive Computing
    Presentation's date: 2008-08-25
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    Information and regulation in decentralized marketplaces for P2P-Grids  Open access

     León Gutiérrez, Xavier; Vilajosana Guillen, Xavier; Brunner, René; Krishnaswamy, Ruby; Navarro Moldes, Leandro; Freitag, Felix; Marquès, Joan Manuel
    IEEE International Workshop on Enabling Technologies: Infrastructure for Collaborative Enterprises
    Presentation's date: 2008-06-23
    Presentation of work at congresses

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    Large scale systems such as the Grid need scalable and efficient resource allocation mechanisms to fulfil the requirements of its participants and applications while the whole system is regulated to work efficiently. Economics inspired models have shown ability to handle efficiently the allocation of resources and services, scaling up well as they are decentralized. Our model considers the arbitration of decisions at the local scope and short term, the regulation of the system at global scope, and the sharing of information between global and local environments. This paper presents a scalable model and evaluates by simulation a system where global market information circulates in aggregated and scalable form, the rate of demand by participants is globally regulated by a currency mechanism, preference is regulated by a reputation mechanism, and local regulation among competing participants is resolved by auction mechanisms. The paper shows how scalable systems benefit from distributed marketplaces supporting global information flow to regulate and optimize local and global behavior.

  • Aplicación Web para la demostración de proyectos

     Freitag, Felix; Liarte, Laura; Navarro Moldes, Leandro; Cabellos Aparicio, Alberto; Guerrero Zapata, Manel
    Congrés Internacional de Docència Universitària i Innovació
    Presentation's date: 2008-07-02
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  • Towards the Development of a Decentralized Market Information System: Requirements and Architecture

     Brunner, René; Freitag, Felix; Navarro Moldes, Leandro
    IEEE International Parallel and Distributed Processing Symposium
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  • Grid Middleware and Services

     Liviu, Joita; Omer, F Rana; Isaac, Chao; Chacin Martinez, Pablo Jesus; Freitag, Felix; Navarro Moldes, Leandro; Ardaiz, Oscar
    Date of publication: 2008-12
    Book

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  • Core services for grid markets

     Chacin Martinez, Pablo Jesus; León Gutiérrez, Xavier; Brunner, René; Freitag, Felix; Navarro Moldes, Leandro
    Date of publication: 2008-07-29
    Book chapter

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  • Core Services For Grid Markets

     Chacin Martinez, Pablo Jesus; Xavier, Leon; Brunner, René; Freitag, Felix; Navarro Moldes, Leandro
    CoreGRID Symposium
    Presentation's date: 2008-08-25
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  • P2PGRID: Self-adjusting Peer-to-peer and Grid Systems (TIN2007-68050-C03-01)

     Chacin Martinez, Pablo Jesus; Navarro Moldes, Leandro; Reyes Muñoz, M. Angélica; Gallardo Gomez, Antonia; Freitag, Felix; Meseguer Pallares, Roque; Royo Valles, Maria Dolores; Artigas Vidal, Pau; Marques Puig, Joan Manel; Sanjeevan, Kanapathipillai; Brunner, René; León Gutiérrez, Xavier; Medina Medina, Esunly
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  • Towards QOS Provision for Virtualized Resources in Grids

     Rodriguez, Fernando; Freitag, Felix; Navarro Moldes, Leandro
    INGRID 2008 Instrumenting the Grid
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  • On the use of intelligent local resource management for improved virtualized resource provision: challenges, required features, and an approach

     Rodríguez, Fernando; Freitag, Felix; Navarro Moldes, Leandro
    Workshop on System-level Virtualization for High Performance Computing
    Presentation's date: 2008
    Presentation of work at congresses

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  • Towards QoS Provision For Virtualized Resources in Grids

     Freitag, Felix
    INGRID 2008 Instrumenting the Grid
    Presentation's date: 2008-04-09
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  • Improving the Introduction to a Collaborative Project-Based Course on Computer Network Applications

     Freitag, Felix; Navarro Moldes, Leandro; Marques Puig, Joan Manel
    Computational Science- ICCS'2008
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  • Uncertainty Management for the Retrieval of Economic Information from Distributed Markets

     Brunner, René; Freitag, Felix; Navarro Moldes, Leandro
    international conference on Scalable Uncertainty Management
    Presentation's date: 2008
    Presentation of work at congresses

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  • Aplicación "Demo proyectos" para mejorar la propuesta de proyectos en una asignatura de proyectos

     Freitag, Felix; Navarro Moldes, Leandro; Cabellos Aparicio, Alberto; Marques Puig, Joan Manel
    Jornadas de Enseñanza Universitaria de la Informática
    Presentation of work at congresses

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  • Autonomous Management in Virtual-machine-based Resource Providers

     Rodriguez, Fernando; Freitag, Felix; Navarro Moldes, Leandro
    IEEE International Conference on Self-Adaptive and Self-Organizing Systems
    Presentation's date: 2008
    Presentation of work at congresses

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  • Aplicación "Demo de proyectos" para mejorar la propuesta de proyectos en una asignatura de proyectos

     Freitag, Felix
    Jornadas de Enseñanza Universitaria de la Informática
    Presentation's date: 2008-07-09
    Presentation of work at congresses

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  • Assessing a Distributed Market Infrastructure for Economics-Based Service Selection

     Brunner, R; Chao, I; Chacin Martinez, Pablo Jesus; Freitag, Felix; Navarro Moldes, Leandro; Ardaiz, O; Joita, L; Rana, O
    Lecture notes in computer science
    Date of publication: 2007-11
    Journal article

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