Departamento de Informática / Department of Informatics (FC-DI)
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Welcome to the publications repository of the Department of Informatics of the University of Lisbon, Faculdade de Ciências.
This repository was built to index, store, and share of the Department's and it's research units – Lasige and LabMAg – intellectual production in digital format, such as: thesis, technical reports, learning objects, etc.
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- Scalable Atomic MulticastPublication . Rodrigues, Luís; Guerraoui, Rachid; Schiper, AndréWe present a new scalable fault-tolerant algorithm which ensures total order delivery of messages sent to multiple groups of processes. The algorithm is scalable in the sense that: (1) any process can multicast a message to one or more groups of processes without being forced to join those groups; (2) inter-group total order is ensured system-wide but, for each individual multicast, the number and size of messages exchanged depends only on the number of addressees; (3) failure detection does not need to be reliable. Our algorithm also exhibits a modular design. It uses two companion protocols, namely a reliable multicast protocol and a consensus protocol, and these protocols are not required to use the same communication channels or to share common variables with the total order protocol. This approach follows a design methodology based on the composition of (encapsulated) micro-protocols
- Connectors for Mobile ProgramsPublication . Wermelinger, Michel; Fiadeiro, JoséSoftware Architecture has put forward the concept of connector to express complex relationships between system components, thus facilitating the separation of coordination from computation. This separation is especially important in mobile computing due to the dynamic nature of the interactions among participating processes. In this paper we present connector patterns, inspired in Mobile UNITY, that describe three basic kinds of transient interactions: action inhibition, action synchronization, and message passing. The connectors are given in COMMUNITY, a UNITY-like program design language which has a semantics in Category Theory. We show how the categorical framework can be used for applying the proposed connectors to specific components and how the resulting architecture can be visualized by a diagram showing the components and the connectors
- Plataforma de comunicação para aplicações distribuídasPublication . Gonçalves, Ricardo Manuel Xavier; Rodrigues, Luís
- Core-TyCO, The Language Definition, Version 0.1Publication . Vasconcelos, Vasco T.; Bastos, RuiThis is the second report on TyCO, a (still) experimental strongly and implicitly typed concurrent object oriented programming language based on a predicative polymorphic calculus of objects, featuring asynchronous messages, objects, and process declarations, together with a predicative polymorphic type system
- Dynamic Channels: A New Methodology for Mobile Computing ApplicationsPublication . Afonso, Ana Paula; Regateiro, Francisco S.; Silva, Mário J.We discuss the software engineering of mobile computing information dissemination systems and introduce dynamic channels, a set of extensions to the conceptual models developed for information channels, capturing mobility-specific requirements. These are used for filtering and setting update order priorities for the information that users intend to monitor, which depends on their location and changes as they roam. We also present a new development methodology for a class of mobile computing applications operating under an information dissemination metaphor. The methodology is based on UML, the OMG standard for object-oriented analysis and design
- ACE: Um Agente de Compras na InternetPublication . Neto, Ana Beatriz; Gouveia, Duarte; Silva, Mário J.Electronic commerce through the Internet is a growing business, but there are still some problems to overcome so that every user can become a buyer. Safe transactions are the most discussed problem, but there are other problems that make shopping on the Internet difficult. When we built ACE (which stands for Agente de Compras Especializado) we aimed at solving one of those problems: finding the product or service that best suits your needs. We designed a scalable model for that purpose (since this software could be used to connect every buyer and every seller on the Internet) and we built a prototype that shows how this model works. We describe our proposed model in detail, based on the software agents paradigm, and the methodology we used to develop it. We conclude with a comparison between ACE and a similar commercial product
- A Multi-Agent Architecture for Decision Making under UncertaintyPublication . Ladeira, Marcelo; Coelho, Helder; Viccari, Rosa MariaAn influence diagram represents a decision problem formalisation where the decision-maker is a rational one; i.e. he prefers the decision that maximises the utility function expected value. This formalism models the domain through a single homogeneous network and without considering the existence of specific sub-domains into the domain at hand. The main goal of this research project is to study the application of the multi-agent approach to the evaluation of influence diagrams, motivated by the intention of exploring the locality propriety in large domains. A domain that has locality can be looked by parts because it has specific and natural sub-domains. The decision-maker that reasons and decides based on the domain information can focus on a single sub-domain each time, and occasionally shift his attention to another sub-domain. This technical report was written when the first author was visiting the Computer Science Department of the University of Lisbon. It is the thesis proposal for the Computer Science doctor degree of the first author at the Brazilian Federal University of Rio Grande do Sul, and it was submitted with success last April
- GwB, A Workbench for Natural Language GrammarsPublication . Branco, António HortaAs an intermediate instrumental step in our research on reference processing and binding theory, we built up a grammar workbench which we called GwB. This workbench was primarily designed as a computational tool to help verifying the theoretical consistency and the empirical adequacy of our working hypotheses. In this paper, we report on the architecture underlying GwB and its functionality. Firstly, we present the general language processing framework embodied in the grammar workbench. Secondly, we present a brief survey of the computational systems available for the implementation of that framework and discuss the major aspects of the implementation of GwB in the system we opted for
- Sistema de suporte à atribuição de recursos em ambientes de rede heterogéneosPublication . dos Santos, António Manuel Gomes; Moreira, Vitor; Veiga, Pedro Manuel Barbosa
- Desenvolvimento de uma aplicação sobre equipamento portuário, para consulta e gestão de dados na internetPublication . Machado, Sérgio Marinho da Cruz; Cláudio, Ana Paula