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- Uma arquitectura IPtel utilizando o protocolo SIPPublication . Sousa, João Paulo; Carrapatoso, EuricoMais e melhores acessos à Internet, bem como um preço atractivo, fazem com que seja cada vez maior o interesse em transportar voz e vídeo sobre redes de dados. Neste contexto nasceu a Telefonia sobre IP, que oferece através desta infra-estrutura a oportunidade de criar sistemas globais de comunicação multimédia. O Session Initiation Protocol, utilizado nesta arquitectura, é um protocolo de sinalização e controlo de chamadas entre dois ou mais participantes. Neste artigo é feita uma apresentação do serviço de Telefonia sobre IP, são analisados diversos protocolos tipicamente usados na arquitectura protocolar da IPtel, e é explicada a arquitectura e o funcionamento do protocolo SIP. São também referidos vários modos de mobilidade disponibilizados pelo SIP ao nível da aplicação. Finalmente são apresentadas algumas características do sIPtel, um sistema IPtel desenvolvido em Java com suporte para vídeo e que utiliza o protocolo SIP na sinalização de chamadas.
- An evolutionary platform for the collaborative contextual composition of servicesPublication . Sousa, João Paulo; Fonseca, Benjamim; Carrapatoso, Eurico; Paredes, HugoBesides services traditionally available in wireless networks, new ones may be offered that transparently adjust and adapt to the user context. The user would have more choice and flexibility if not only could he use platform and third-party services, but also compose his own services in an ad-hoc way, making it available to other users, involving them collaboratively in the construction of a wide set of services. Moreover, collaboration among users can be fostered by the availability of awareness services in mobile environments that enable them to execute joint tasks and activities. This paper presents iCas, an architecture to create context-aware services on the fly, and discusses its main modules. Also a collaborative application scenario is briefly described.
- A service-oriented middleware for composing context aware mobile servicesPublication . Sousa, João Paulo; Fonseca, Benjamim; Carrapatoso, EuricoRecent advances in wireless networks and mobile devices have brought about new scenes for the provision of services to end-users. Besides traditional services, new ones may be provided that transparently adjust and adapt to the user context. The user would have more choice and flexibility if, besides using the services, he could also compose his own services in an ad-hoc way. This paper presents iCas, an architecture to create context-aware services on the fly and discusses its main components. Also an application scenario is briefly described.
- An IPtel architecture based on the SIP protocolPublication . Sousa, João Paulo; Carrapatoso, EuricoMore and better accesses to the Internet increase the interest in using it to carry not only data but also voice and video. The IP Telephony (IPTel) was born in this context and offers a framework to create multimedia communication systems. The Session Initiation Protocol, used in the IPTel architecture, is a protocol for signaling and call control between two or more participants. This paper presents telephony over IP service. Different protocols typically used in IPtel are analyzed and the architecture and functionality of SIP protocol are explained. Different mobility modes provided by SIP through the application layer are described. Finally we present the sIPtel, a Java application that supports real audio and video communications and uses the SIP protocol for call signaling.
- SAGA reloaded: towards a generic platform for developing cooperative applicationsPublication . Fonseca, Benjamim; Paredes, Hugo; Sousa, João Paulo; Martins, F. Mario; Carrapatoso, EuricoGroupware specification and development has always been a complex task, requiring special attention to issues such as notification of cooperative actions and ensuring consistency of shared data. Some years ago SAGA was developed as a framework to build groupware applications based on a set of core web services that provide the most common cooperative functionalities. Despite its potential, the last few years brought some technological developments that placed new challenges. This paper presents a new generation of the SAGA platform that adds to the original framework features that emerged recently, namely the regulation of social interaction, incorporation of new communication technologies, connectors to several external services and interaction environments, and the addition of contextual information.
- Uma arquitectura para a composição dinâmica de serviços dependentes do contextoPublication . Sousa, João Paulo; Carrapatoso, Eurico; Fonseca, BenjamimA difusão das ligações sem fios nos locais de trabalho, de lazer e mesmo em casa, juntamente com a proliferação dos dispositivos móveis abrem novos cenários para o fornecimento de serviços aos utilizadores. Além dos serviços tradicionais de Internet devem por isso, ser disponibilizados novos serviços que de uma forma transparente se adeqúem e se adaptem ao contexto do utilizador. Os utilizadores teriam ainda mais flexibilidade e escolha se, para além do fornecimento de destes serviços, lhes fosse dada a possibilidade de eles próprios comporem novos serviços com base em serviços já existentes. Este artigo discute os componentes essenciais de um sistema context-aware que permite a composição dinâmica de serviços sensíveis ao contexto e propõe uma arquitectura possível para implementação desses serviços.
- Composition of context aware mobile services using a semantic context modelPublication . Sousa, João Paulo; Carrapatoso, Eurico; Fonseca, Benjamim; Pimentel, Maria da Graça; Bulcão-Neto, RenatoContext-awareness has been regarded as an important feature for mobile services. However, only a few services are sensible to context and the features that are context-aware are still limited. Composition of Web services has received much interest in business-to-business or enterprise application, but not so much interest in business-to- consumer applications. This paper presents iCas, a novel architecture that enables the creation of context-aware services on the fly, and discusses its main components. We compare our approach with similar systems and point out the main differences and advantages. To explore context-awareness to support service composition, iCas uses SeCoM, a semantic model to represent context. The main parts of this model are explained as well the advantages of using a semantic model to represent context. We also describe the use of our approach in an university campus to provide pedagogical features and assist the socio-pedagogical interaction of various types of users.