Fig 2 - uploaded by Angelo Brayner
Content may be subject to copyright.
Source publication
In an environment with support for mobile computing, we may have a collection of autonomous, distributed, heterogeneous and mobile databases, denoted Mobile Database Community (MDBC), in which each database user can access databases in the community through a wireless communication infrastructure. In such an environment, new participants may join t...
Context in source publication
Context 1
... that purpose, the runner agent should migrate to the remote mobile unit in which the query should be executed. Figure 2 depicts an abstract model of the query engine for processing global (dis- tributed) and remote queries. According to the proposed engine, a query is processed by six distinct phases: Pre-Processing, Decomposition, Context Recognition, Clone Generation, Fragment Execution and Post-Processing phases. ...
Citations
... In other words, by means of this notion, we want to capture the fact that some transactions present a serial execution of atomic units. It does not mean that our model requires that transactions should be partitioned into smaller pieces as proposed in [3] and [4]. ...
... The two protocols have been implemented to be integrated to the accessing mobile databases (AMDB) architecture [4]. The key goal of the AMDB is to enable mobile database communities (MDBCs) to be formed opportunistically over mobile databases residing on mobile hosts which are nodes of a MANET and to make mobile databases belonging to the formed MDBC interoperable. ...
The topology of a mobile ad hoc network (MANET) may change randomly and rapidly at an unpredictable time, since nodes are free to move arbitrarily. In such an environment, we may have a collection of autonomous, distributed, heterogeneous and mobile databases (denoted mobile database community (MDBC)). This paper describes an approach for controlling concurrency of mobile transactions executed in MDBCs. The proposed approach is based on the use of semantic knowledge to relax the notion of absolute transaction atomicity. Supported by this new concept of atomicity, we propose a new correctness criterion, denoted mobile semantic serializability, for the execution of concurrent transactions in MDBCs. The proposed correctness criterion provides a high degree of inter-transaction parallelism and ensures consistency of the mobile database.
Integrating data sources published on the Web requires an integration strategy that guarantees the local data sources' autonomy. A multidatabase system (MDBS) has been consolidated as an approach to integrate multiple heterogeneous and distributed data sources in flexible and dynamic environments such as the Web. A key property of MDBSs is to guarantee a higher degree of local autonomy. In order to adopt the MDBS strategy, it is necessary to use a query language, called the MultiDatabase Language (MDL), which provides the necessary constructs for jointly manipulating and accessing data in heterogeneous data sources. In other words, the MDL is responsible for solving integration conflicts. This chapter describes an extension to the XQuery Language, called MXQuery, which supports queries over several data sources and solves such integration problems as semantic heterogeneity and incomplete information.
New achieves in wireless network technology, satellite services and cellular communication allows to usage of mobile computing. This mobility is troublesome for doing mobile computing that need to retrieve information from database. System movement during transaction execute, causes to disconnection of mobile unit from wireless network and this disconnection due to transaction abort and mobile system have to redo transaction from start. One of methods that used to prevention of transaction abort is using of cache in mobile units. The information that need to current transaction execution, are saved in cache. Prediction and sending Appling additional information for mobile unit in order to prevention of transaction abort during disconnection of mobile system with wireless network. Our goal of this work is present a solution for prediction information for send to mobile unit in order to use cache operation with usage Fuzzy theory.
There are many issues concerning the effective use of mobile systems, both in respect of the current technology and those likely to become available in the near future. For mobile databases the most important of these issues are: • The relative unreliability of connections (and the variability of bandwidth when connected), • The limitations on storage capacity, and • The security and privacy issues created when a computer is in a mobile environment. One of methods of prevention of transaction aborts prediction and sending. Appling additional information for mobile system in order to prevention of transaction aborts during disconnection of mobile system with wireless network until connection with the next wireless network during mobilization. The goal of this work is presentation of solution for prediction information for sending mobile system in order to use cache operation with usage Genetic algorithms.
In a mobile ad hoc network (MANET) nodes are free to move arbitrarily. The nodes represent mobile computers in which database systems may reside. In such an environment, we may have a collection of autonomous, distributed, heterogeneous and mobile databases (denoted Mobile Database Community or MDBC), where each database user (in a mobile host) can access databases of the collection through the MANET. Traditional query processing techniques fail to support the access to databases in an MDBC, since data delivery rate in such an environment becomes unpredictable and mobile hosts may suffer from limited available main memory to process some query operators (e.g., join). To react to those events, we propose an adaptive operator, called MobiJoin, for processing join operations on mobile databases in an MDBC. MobiJoin ensures: (i) incremental production of results as soon as the data become available; (ii) progress of the query processing even when the delivery of data is blocked, and; (iii) reaction to situations of memory limitation on the execution of operator. Cost estimation and experimental results of the MobiJoin are presented to evidence that the proposed operator is an effective solution for processing join on mobile databases.
Resumo As recentes evoluções ocorridas nos computadores portáteis em conjunto com os avanços nas tecnologias de comunicação sem fio estão possibilitando que os usuários de dispositivos móveis mantenham a conexão com a rede enquanto se movimentam livremente, tendo acesso a recursos, serviços e informações compartilhadas. Este paradigma computacional é denominado de computação móvel. A computação móvel possibilita o desenvolvimento de novas e sofisticadas aplicações em banco de dados. Tais aplicações necessitam recuperar dados atuais e consistentes. Entretanto, devido às limitações inerentes aos ambientes móveis, como reduzida largura de banda e freqüente desconexão dos dispositivos portáteis, torna-se necessário que mudanças no gerenciamento e nos mecanismos de garantia de consistência dos dados sejam implementadas. Este trabalho investiga, descreve e classifica as principais abordagens para manter a consistência dos dados em ambientes de computação móvel. 1. Introdução A integração dos computadores portáteis com as recentes tecnologias de comunicação celular, redes de comunicação sem fio e serviços via satélite está possibilitando que os usuários de dispositivos móveis mantenham a conexão com a rede enquanto se movimentam livremente, tendo acesso a recursos, serviços e informações compartilhadas. Este paradigma computacional é denominado de computação móvel. Neste ambiente, os usuários têm acesso a informações e recursos compartilhados independente de onde estejam localizados e de sua mudança de localização (mobilidade). A computação móvel possibilita o desenvolvimento de novas e sofisticadas aplicações em banco de dados. Entretanto, para que estas aplicações possam executar de forma efetiva, torna-se necessário que mudanças no gerenciamento e nos mecanismos de garantia de consistência dos dados sejam implementadas. Essa necessidade surge das restrições impostas pelos ambientes de comunicação sem fio, tais como: Limitação na largura de banda dos canais de comunicação sem fio, mobilidade e freqüentes desconexões dos dispositivos móveis, mobilidade dos dados e grande número de usuários. O gerenciamento de dados e o controle de concorrência em ambientes de computação móvel tem sido objeto de uma variedade de pesquisas e produtos comerciais. Novos modelos computacionais, arquiteturas, modelos transacionais, protocolos e algoritmos têm sido propostos. Neste trabalho, fazemos uma revisão bibliográfica das principais abordagens propostas para garantir a consistência dos dados em ambientes de computação móvel e propomos uma taxonomia a fim de classificar e organizar estes trabalhos. Além disso, apresentamos em detalhes como o sistema Bayou [40, 41, 42, 43] pode ser utilizado para garantir a consistência dos dados em redes móveis fracamente (parcialmente) conectadas, garantindo alta disponibilidade de dados.
Flexible and dynamic environments are characterized by high independence from connection participants, low control over available services and high tolerance to communication failures. Integrating data sources published on such environments requires an integration strategy that guarantees local data sources autonomy. Multidatabase System (MDBS) has been consolidated as an approach to integrate multiple heterogeneous and distributed data sources. A key property of MDBSs is to guarantee a higher degree of local than the other approaches for integrating heterogeneous data sources. MDBS technology uses a query language as integration mechanism, which is responsible for solving integration conflicts. Thus, the query language must provide constructs to perform queries over several different data sources. Furthermore, it should be capable for solving integration conflicts. This paper proposes an extension to the XQuery language, called MXQuery. The key feature of the proposed language is to provide mechanisms, which support the capability to jointly manipulate data in different data sources based on an XML data model.
New advantages in wireless network technology, satellite, services and cell connection provide permit ion of usage of mobile computing . this mobilization is troublesome for doing mobile computing is related to resaving information from database mobilization the system during transaction causes of disconnection of mobile system with wireless network users and this disconnection due to transaction abort and mobile system have to redo transaction from start. One of methods of prevention of transaction abort prediction and sending applying additional information for mobile system in order to prevention of transaction abort during disconnection of mobile system with wireless network until connection with the next wireless network during mobilization .our goal of this work is presentation of solution for prediction information for sending mobile system in order to use cache operation with usage Genetic algorithms.
A new approach for caching data objects and locks by a centroid from a server in a cluster of peers using ad hoc transactions is presented. A cluster of peers is formed by a set of mobile hosts, which are clustered around a single mobile host called a centroid. A set of mobile hosts are called peers. A centroid is formed as a temporary work group for processing and exchanging information. In life cycle of a mobile transaction processing system, data is cached from the server and a centroid is disconnected from the server to create its own cluster of peers. A dynamically configurable data processing space, called an envelope repository, is created to process various transactions at the centroid. The processed data is kept in an envelope at the private work space of the centroid and is brought to the envelope repository whenever required.
This paper presents a mobile transaction model for supporting mobile collaborative works. The mobile transaction processing system supports data sharing among mobile hosts via the concept of mobile affiliation workgroups. Data sharing among mobile transactions in a mobile affiliation workgroup is supported by export and import transactions in an export-import repository, which is a mobile sharing workspace. This means that the data sharing process is divided into smaller transaction processes and separated from the main transactions. The mobile transaction system also distinguishes two different mechanisms for supporting data sharing in mobile environments, which are sharing data states and sharing data status.
