Transmission of continuous query results in mobile computing systems

Cataloged from PDF version of article.In a mobile computing environment, a user with a wireless connection to the information network can access data via submitting queries to data servers. As the mobility is the most distinguishing feature of the mobile computing paradigm, location becomes an important piece of information for the so-called location-dependent queries, where the answer to a query depends on the current location of the user who issued the query. A location-dependent query submitted by a mobile user can become more difficult to process when it is submitted as a continuous query (CQ) for which the answer changes as the user moves. The answer to a location-dependent CQ can be provided as a set of tuples [S, begin, end] indicating that object S is the answer of the query from time begin to time end. Once the tuples in the answer set are determined, the next step is to determine the transmission time of these tuples to the user. Transmission time of tuples is critical in the sense that it can have a considerable impact on both the communication overhead imposed on the wireless network and the availability of tuples in case of disconnections. In this paper, we propose three tuple transmission approaches that can be used to determine the transmission time of tuples in the answer set of a location-dependent CQ. We also evaluate the relative performance of the proposed approaches under different settings of environmental parameters. (C) 2000 Elsevier Science Inc. All rights reserved

Visitor: um sistema de informação dependente da localização

Os sistemas de informação com carácter de mobilidade oferecem novas possibilidades aos utilizadores, nomeadamente em relação aos serviços de que estes podem usufruir. Este tipo de modelo de sistemas de informação possui características que resultam em questões que não eram comuns nos sistemas de informação tradicionais. As fontes de informação são heterogéneas, dispersas, desconhecidas e associadas a localizações físicas. O próprio carácter de mobilidade acarreta consigo as questões que lhe são inerentes, como a localização e inconstância da conectividade. Este artigo descreve um sistema de informação dependente da localização, apresentando as soluções desenvolvidas para lidar com as questões próprias a este tipo de ambiente

Enhancing Information Retrieval Relevance Using Touch Dynamics on Search Engine

Using Touch Dynamics on Search Engine is an attempt to establish the possibilities of using user touch behavior which is monitored and several unique features are extracted. The unique features are used for identifying users and their traits according to the touch dynamics. The results can be used for defining automatic user unique searching behavior. Touch dynamics has been discussed in several studies in the context of user authentication and biometric identification for security purposes. This study establishes the possibility of integrating touch dynamics results for identifying user searching preferences and interests. This study investigates a technique of combining personalized search with touch dynamics results information as an approach for determining user preferences, interest measurement and context. Keywords: Personalized Search, Information Retrieval, Touch Dynamics, Search Engin

Mobile transaction management in mobisnap

Lecture Notes in Computer Science, 1884To allow mobile users to continue their work while disconnected, mobile systems usually rely on optimistic replication techniques. In mobile database systems, mobile units cache subsets of the database state and allow disconnected users to perform transactions concurrently. These transactions are later integrated in the master database state. As concurrently performed transactions may conflict, it is usually impossible to determine the result of an update in the mobile unit. Moreover, this model differs from the traditional client/server model due to the fundamental fact that the user will usually not be connected to the system when the results of his transactions are finally determined - therefore, he can not immediately perform adequate alternative actions. In this paper we describe a transaction management system that takes into consideration the above-mentioned characteristics. Transactions are specified as mobile transactional programs, which allows the precise definition of operation semantics and the definition of alternative actions. Support for active user notification is also provided in the system. Finally, the system relies on a reservation mechanism to be able to guarantee the results of transactions in the mobile units.(undefined

AN ATTEMPT TO DEFINE CONTEXT AWARENESS IN MOBILE E-HEALTH ENVIRONMENTS

Nurses, doctors, physiotherapists, psychologists and other professionals or specialists come together to provide care to home residing patients, making continuous assessment, diagnosis and treatment possible beyond the walls of hospitals. Such teams of professionals are focused on each individual patient, and are virtual, i.e. they make decisions without being together physically, dynamically, i.e. professionals come and go as needed, and collaborate, as they combine their knowledge to provide effective care. Our system, coined DITIS, is a web based system that enables the effective management and collaboration of virtual healthcare teams and accessing medical information in a secure manner from a variety of mobile devices from anytime and anyplace, adapting the information according to various parameters like, user role, access right, device capabilities and wireless medium. This paper introduces the DITIS system, and identifies the needs and challenges of co-ordinated teams of multidisciplinary healthcare professionals (HCPs) functioning in a context awareness environment under the wireless environment. Pilo

Performances de protocoles transactionnels en environnement mobile

National audience. L'omniprésence d'unités mobiles et le développement des réseaux sans fil motivent des avancées en matière de supports d'exécution pour une grande variété d'applications en envi-ronnement mobile. Des efforts importants sont faits pour offrir une bonne gestion des données malgré les caractéristiques limitées de tels environnements. La notion de transaction a été ré-étudiée pour proposer des modèles et des protocoles permettant d'assurer certaines propriétés transactionnelles. Les algorithmes et protocoles proposés tentent d'optimiser l'utilisation des ressources des unités mobiles et de surmonter les limitations du réseau mobile. Dans cet article nous nous intéressons spécifiquement aux protocoles de validation de transactions réparties sur plusieurs unités dont certaines mobiles. Nous présentons ici les résultats d'un travail qui iden-tifie des propriétés qualitatives et des indices de performance quantitatifs, et étudie ceux-ci sur quatre protocoles (2PC, UCM, CO2PC et TCOT). Trois de ces protocoles sont des propositions spécifiques pour des environnements mobiles et sont représentatifs des propositions actuelles. Nous nous intéressons à la phase de validation des transactions, ainsi qu'à l'influence des dif-férents protocoles sur les performances du déroulement de l'ensemble des transactions. ABSTRACT. This is an abstract. The omnipresence of mobile devices and wireless networks lead to a growing interest in supporting a wide variety of applications in mobile environments. Numerous efforts in providing appropriate data managements for such environments are made. Transaction supports have been revisited to propose adapted transaction models and properties. Proposed algorithms and protocols try to optimise the use of mobile units resources and to overcome wireless network limitations. This work concerns protocols to commit transactions distributed over several mobile and fixed units. Results presented here concern the identification of qualitative properties and quantitative performance indices that are studied on four protocols (2PC, UCM, CO2PC et TCOT). Three of them are specifics propositions for mobile environments and are representative of current proposals. The analysis concerns the transaction validation phase as well as the impact of the protocols on the performances during a transaction execution itself. MOTS-CLÉS : transactions mobiles , evaluation de performances, protocoles de validation

Mobile Database System: Role of Mobility on the Query Processing

Abstract-The rapidly expanding technology of mobile communication will give mobile users capability of accessing information from anywhere and any time. The wireless technology has made it possible to achieve continuous connectivity in mobile environment. When the query is specified as continuous, the requesting mobile user can obtain continuously changing result. In order to provide accurate and timely outcome to requesting mobile user, the locations of moving object has to be closely monitored. The objective of paper is to discuss the problem related to the role of personal and terminal mobility and query processing in the mobile environment