ESTGV - DI - Documentos de congressos (comunicações, posters, actas)
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- e-Consultation as a tool for participation in teachers’ unions: the greater the focus, the greater the number of visitsPublication . Quental, Carlos; Gouveia, Luis BorgesIn the 2000’s, the Internet became the preferred mean for the citizens to communicate. The YouTube, Twitter, Facebook, LinkedIn, i.e., the social networks in general appeared together with the Web 2.0, which allows an extraordinary interaction between citizens and the democratic institutions. The trade unions constantly fight governments’ decisions, especially in periods of crisis like the one that the world, Europe and, in particular, Portugal are facing. In this regard, the use of e-participation platforms is expected to strengthen the relationship between trade unions and the education community. This paper reports the research about the planning and driving of a series of experiments of online public consultation, launched by teachers’ trade unions. These experiments are compared with those of other countries, such as Australia, United Kingdom and United States of America. A quantitative analysis of the results regarding hits, subscriptions, and response rates is presented, and it is compared with the 90-9-1 rule, the ASCU model and data from government agencies. The experiments performed used the Liberopinion, an online platform that supports bidirectional asynchronous communication. A better understanding of the benefits of these collaborative environments is expected by promoting quality of interaction between actors.
- SHStream: Self-Healing Framework for HTTP Video-StreamingPublication . Cunha, Carlos Augusto da Silva; Silva, Luis M.HTTP video-streaming is leading delivery of video content over the Internet. This phenomenon is explained by the ubiquity of web browsers, the permeability of HTTP traffic and the recent video technologies around HTML5. However, the inclusion of multimedia requests imposes new requirements on web servers due to responses with lifespans that can reach dozens of minutes and timing requirements for data fragments transmitted during the response period. Consequently, web- servers require real-time performance control to avoid playback outages caused by overloading and performance anomalies. We present SHStream , a self-healing framework for web servers delivering video-streaming content that provides (1) load admit- tance to avoid server overloading; (2) prediction of performance anomalies using online data stream learning algorithms; (3) continuous evaluation and selection of the best algorithm for prediction; and (4) proactive recovery by migrating the server to other hosts using container-based virtualization techniques. Evaluation of our framework using several variants of Hoeffding trees and ensemble algorithms showed that with a small number of learning instances, it is possible to achieve approximately 98% of recall and 99% of precision for failure predictions. Additionally, proactive failover can be performed in less than 1 second
- Reboot-based Recovery of Performance Anomalies in Adaptive Bitrate Video-Streaming ServicesPublication . Cunha, Carlos Augusto da Silva; Silva, Luis M. ePerformance anomalies represent one common type of failures in Internet servers. Overcoming these failures without introducing server downtimes is of the utmost importance in video-streaming services. These services have large user abandon- ment costs when failures occur after users watch a significant part of a video. Reboot is the most popular and effective technique for overcoming performance anomalies but it takes several minutes from start until the server is warmed-up again to run at its full capacity. During that period, the server is unavailable or provides limited capacity to process end-users’ requests. This paper presents a recovery technique for performance anomalies in HTTP Streaming services, which relies on Container-based Virtualization to implement an efficient multi-phase server reboot technique that minimizes the service downtime. The recovery process includes analysis of variance of request-response times to delimit the server warm-up period, after which the server is running at its full capacity. Experimental results show that the Virtual Container recovery process completes in 72 seconds, which contrasts with the 434 seconds required for full operating system recovery. Both recovery types generate service downtimes imperceptible to end-users.
- Dynamic enhancement of videogame soundscapesPublication . Pires, Durval; Alves, Valter; Roque, LicinioA game soundscape often includes sounds that are triggered by the game logic according to the player’s actions and to other real time occurrences. The dynamic nature of such triggering events leads to a composition that is not necessarily interesting, at a given moment. We propose a system aiming at the enhancement of the soundscape generated during gameplay. The main component of the system is a module that implements heuristics, which we set to follow principles from Acoustic Ecology and, specifically, the notion of healthy soundscape. In order to inform the heuristics, designers can characterize the sounds being handled by the sound engine, using an API that aims to be accessible and informative about the designer’s intentions. We also present reflections on an essay where a game was remade using the proposed system, which helped us to support the feasibility of the proposed system.
- A Software Architecture for Dynamic Enhancement of Soundscapes in GamesPublication . Pires, Durval; Alves, Valter; Roque, LicinioDespite an emerging interest in the application of dynamic computer music systems to computer games, currently there are no commonly accepted approaches to empirically evaluating game music systems. In this paper we pose four questions that researchers could assess in order to evaluate different aspects of a game music system. They focus on the music's effect on the game playing experience (whether the music leads to a more enjoyable experience, and whether it affects the player in the intended way during the game), and how the music itself is perceived (whether it reaches a certain aesthetic standard, and whether it accurately conveys the intended narrative). We examine each of these questions in turn, for each one establishing a theoretical background as well as reviewing and comparing relevant research methodologies in order to show how it could be addressed in practice.
- Visualização Dinâmica de Nuvens Através de Diagramas TermodinâmicosPublication . Duarte, Rui P.; Morgado, José Francisco; Gomes, Abel J. P.A simulação e renderização de fenómenos naturais tem sido um dos grandes desafios em computação gráfica devido às suas aplicações em filmes de animação, ambientes virtuais e jogos. Este problema advém do facto de a formação, movimento e extinção de nuvens serem, naturalmente, processos amorfos e dinâmicos. Este artigo propõe-se a resolver este problema através de diagramas termodinâmicos SkewT/LogP. Estes diagramas constituem uma técnica 2D para simular nuvens em 3D a partir de dados atmosféricos disponibilizados por agências meteorológicas. Para atingir taxas de tempo real, o nosso sistema baseia-se na física, mas evita resolver equações diferenciais para representar, controlar, simular e renderizar o processo termodinâmico da ascensão de nuvens na atmosfera
- Esquema de Multiresolução para Aplicações Geométricas em Tempo RealPublication . Rodrigues, Rui; Morgado, José Francisco; Silva, Frutuoso; Gomes, AbelEste artigo descreve um novo esquema multiresolução que manipula a geometria e topologia duma forma separada. A sua estrutura de dados designa-se por estrutura de dados baseada na aresta fantasma. Este esquema recorre a um critério topológico (não a um critério geométrico, como e ́ usual) para simplificar a malha mais rapidamente, o que deixa em aberto a sua utilização em aplicações em tempo real.
- Policy Based and Trust Management for Critical Infrastructure ProtectionPublication . Caldeira, Filipe; Monteiro, Edmundo; Simões, PauloCritical infrastructure (CI) services are consumed by the society constantly and we expect them to be available 24 hours a day. A common definition is that CIs are so vital to our society that a disruption or destruction would have a severe impact on the social well-being and the economy on a national and an international level. CIs can be mutually dependent on each other and a failure in one infrastructure can cascade to another interdependent infrastructure to cause service disruptions. Methods to better assess and monitor CIs and their interdependencies in order to predict possible risks have to be developed. This work addresses the problem of the quality of information exchanged among interconnected CI, the quality of the relationship in terms of trust and security and the use of Trust and Reputation management along with the Policy Based Management paradigm is the proposed solution to be applied at the CI interconnection points for information exchange.
- Trust and Reputation for Critical Infrastructure ProtectionPublication . Caldeira, FilipeToday’s critical infrastructures (CIs) depend on information and communication technologies (ICTs) to deliver their services with the required level of quality and availability. ICT security plays a major role in CI protection and risk prevention for single and also for interconnected CIs were cascading effects might occur because of the interdependencies that exist among different CIs. Among the problems inherent to the operation of Critical Infrastructures, it is possible to emphasise the existence of dependencies and interdependencies among infrastructures. For example, a telecommunications service is inherently dependent on the electricity supply or, for instance, banking services are dependent on both telecommunications and energy supply services. Many of the existing approaches to security in Critical Infrastructures are focused on obtaining risk levels through the use of models based on the infrastructure. Although these models allow a solid foundation for risk monitoring, they do not have mechanisms for exchange, management and assessment of its quality. This presentation addresses the problems related to trust, reputation and risk alerts management within Critical Infrastructures. Accordingly, it is described how to introduce mechanisms to manage and measure at each instant, the degree of confidence assigned to each of the alerts received or computed internally. Allowing improvement of their accuracy and consequently improving the resilience of Critical Infrastructures when faced with inaccurate or inconsistent risk alerts. The lecture’s main goals are to address the problems related to interdependent Critical Infrastructure security and to identify the main problems related to risk information sharing. In particular, how to allow information sharing in a secure manner, the management of that sharing and how to assess the reliability of such information. The European Project MICIE is presented in order to contextualise the presented work. The application of Policy Based Management mechanisms for the management of the risk alert information shared among Critical Infrastructures is described. In order to improve the information sharing management and the further interpretation of the risk alerts, it is described how to evaluate Trust and Reputation in order to assess the shared information and also to consider the behaviour of the entities involved. Selected application scenarios for the presented approaches will be discussed. In particular the integration of those approaches within the MICIE Project and also the integration of the trust and reputation indicators within the CI security Model.
- A policy-based approach to firewall managementPublication . Caldeira, Filipe; Monteiro, EdmundoThis paper describes a policy-based approach to firewall management. The Policy-Based Networking (PBN) architecture proposed by the Policy Framework Group of IETF is analysed, together with the communication protocols, policy specification languages, and the necessary information models. The paper continues with a description of an application of the PBN architecture to firewall management. The proposed architecture is presented and its implementation issues are analysed with some usage examples. The paper concludes with the evaluation of the policy-based approach to firewall management.