Location-based Information Access in Pervasive Computing Environments

普适计算环境中基于位置的信息访问基于位置的空间查询(LBQ)指的是一组基于用户当前位置检索信息的空间查询。由于普适计算环境中用户的无限制移动性，LBQ有别于传统的空间查询。例如，旅行者可能会发出查询“为我查找最近的三家餐厅”。这个问题的答案取决于旅行者接收查询结果的位置。该研究项目的目标是探索新的空间数据索引和缓存方法，以支持普适计算中LBQ的处理，并通过分析、实现和模拟来验证该项目所获得的方法。该项目的重点是特别适合于无线数据广播的方法。该项目研究了一系列LBQ查询，包括点查询、窗口查询、最近邻(NN)搜索、k近邻(KNN)搜索、连续最近邻(CNN)搜索、空间连接和复杂查询。解决了所有空间索引和缓存方案所面临的基本问题(如大索引搜索空间、大索引大小、无线数据广播的线性流特性、移动用户的连续移动和请求以及缓存替换/失效)。这一研究成果将对空间数据库和普适计算领域的发展产生重大影响。拟议的研究活动将与PI在本科生和研究生阶段的教育目标和活动密切结合。开发的技术和实验数据将通过网站及时提供，并在多学科和跨学科的会议、讲习班和期刊上发表。此外，在可能的情况下，将向更广泛的社区，包括公众或行业，介绍科学和工程知识。最后，本研究获得的结果和经验在基于位置的服务中有许多可能的应用，例如基于最近宣布的SPOT技术和直接频带网络的服务。出版物、技术报告、软件和实验数据可在项目网站http://www.cse.psu.edu/pda/LBSQ上查阅

Location-based Information Access in Pervasive Computing EnvironmentsLocation-based spatial queries (LBSQs) refer to a set of spatial queries that retrieve information based on the current locations of the users. Due to the unrestricted mobility of users in the pervasive computing environments, the LBSQs is distinct from the traditional spatial queries. For example, a traveller may issue a query "find me the three nearest restaurants". The answer to this query is dependent on the location where the traveller receives the query results. The goal of this research project is to investigate new ways of indexing and caching spatial data to support processing of LBSQs in pervasive computing and to validate the methods obtained from this project via analysis, implementation, and simulations. The emphasis of the project is on methods that are particularly suitable for wireless data broadcast. A list of LBSQs, including point query, window query, nearest neighbor (NN) search, k nearest neighbor (KNN) search, continuous nearest neighbor (CNN) search, spatial join, and complex queries is studied in this project. Fundamental issues faced by all the spatial indexes and caching schemes (such as large index search space, large index size, linear streaming property of wireless data broadcast, continuous movement and requests of mobile users, and cache replacement/invalidation) are tackled. This research result will have significant impacts on advancing the fields of spatial databases and pervasive computing. The proposed research activities will be closely integrated with the PI's educational goals and activities at both of the undergraduate and graduate levels. The developed techniques and experimental data will be made available in a timely manner by means of a website and publication in multi- and interdisciplinary conferences, workshops, and journals. In addition, scientific and engineering presentations will be given to the broader community, including the public or industry, where possible. Finally, the results and experiences obtained in this research have many possible applications in location-based services, e.g., those based on the recently announced SPOT technology and directband network. Publication, technical reports, software and experimental data can be accessed at the project web site http://www.cse.psu.edu/pda/LBSQ