Middleware Components to Support Mobile Users in Heterogeneous Environments

移动用户需要类似于传统台式计算机提供的功能。这包括访问分布式、异类信息源的能力。然而，提供对分布式信息源的透明访问的现有方法是面向固定网络的，没有考虑到移动用户的具体需要。这些需求的根源在于两个特点：移动性和连通性差。但为了满足这些需求，用于提供对信息源的透明访问的中间件组件必须经过仔细的调整。有鉴于此，我们的研究将扩展最流行的范例的中间件组件，以提供对异类信息源(即，中介体系结构)的透明访问，以满足移动用户的需求。特别是，我们的研究将集中在四个主要主题上：(1)引入位置感知交易服务，其允许移动用户不仅基于中介提供的内容而且基于从当前用户位置访问它的容易程度来找到合适的中介来回答查询，(2)引入能够处理位置相关查询的中介，(3)开发一种管理中介的管理策略，管理中介的生成和复制以及结果的物化；(4)开发支持位置相关和无线查询的接口代理。通过这些扩展，基于中介的系统将完全支持移动用户，从而使他们能够透明地访问异质、分布式的信息源。目标应用包括旅行销售人员访问其公司的信息源、在该领域工作的科学家访问基于互联网的数据库、急诊医生访问患者信息以及处理自然灾害的紧急人员的信息需求。

Mobile users require a functionality similar to that provided by traditional desktop computers. This includes the ability to access distributed, heterogeneous information sources. Yet existing approaches to providing transparent access to distributed information sources are geared towards fixed networks and do not take into account specific needs of mobile users. These needs have their roots in two characteristics: mobility and poor connectivitiy. But in order to meet these needs, middleware components used to provide transparent access to information sources have to be adapted consideralby. In view of this, our research we will extend the middleware components of the most popular paradigm to providing transparent access to heterogeneous information sources, (viz., the mediator architectures) to meet the needs of mobile users.In particular our research will focus on four main topics: (1) the introduction of a location-aware trading service that allows mobile users to find the appropriate mediator to answer a query based not only on the contents offered by the mediator but also on how easily it is accessible from the current user location, (2) the introduction of mediators capable of handling location-dependent queries, (3) the development of a management strategy for mediators that governs the generation and replication of mediators and the materialization of results, and (4) the development of an interface agent supporting location-dependent and wireless querying.With these extensions, mediator-based systems will fully support mobile users, thus allowing them the im-portant transparent access to heterogeneous, distributed information sources. Targeted applications include traveling salespersons accessing their companies' information sources, scientists working in the field accessing internet-based databases, emergency physicians accessing patient information and the information needs of emergency personnel handling natural disasters.