COMET: An Efficient and Scalable Trajectory Data Management System

位置感知设备的使用，如带有GPS的手机或带有RFID（无线射频识别）标签的物体，在许多新兴的时空应用中呈爆炸式增长。传统的数据库管理系统（DBMS）并不是为处理这样的应用程序而设计的，特别是当应用程序需要管理大量移动对象时。COMET（不断发展轨迹的持续管理）项目的目标是设计、实现和构建一个数据库管理系统，用于管理不断发展轨迹数据集的大型存储库。由于在这些环境中位置更新是不断发布的，因此DBMS必须支持极其有效的方法来处理更新。此外，为了允许查询移动对象以前的位置，DBMS必须跟踪过去的轨迹。随着时间的推移，这些轨迹的长度继续增加，并且随着移动对象数量的增加，数据库的大小可能会急剧增加。因此，后端DBMS必须部署可扩展的技术来处理不断增加的数据大小和不断增加的移动对象数量。COMET项目的重点是开发高效且可扩展的方法，用于查询移动对象的过去、现在和未来位置，以及在此环境中可扩展的触发机制。这一项目的预期结果可能对新兴的基于通知的应用产生重大影响，例如应急响应系统，在这些应用中，关键数据需要根据用户当前和不断变化的空间位置向实际移动用户传播。该项目还将培养一批研究生和本科生。项目网站（http://www.eecs.umich.edu/~jignesh/comet）将用于向广泛的研究社区免费提供COMET软件、所有开发的应用程序和真实的用户移动数据。

The use of location-aware devices, such as cell phones with GPS or objects with RFID (Radio Frequency Identification) tags, is exploding in a number of emerging spatio-temporal applications. Traditional database management systems (DBMS) are not designed to handle such applications, especially if the application requires managing a large number of moving objects. The goal of the COMET (Continuous Management of Evolving Trajectories) project is to design, implement, and build a database management system for managing large repositories of continuously evolving trajectories data sets. Since in these environments location updates are issued continually, the DBMS must support extremely efficient methods for dealing with updates. In addition, to allow querying on previous locations of the moving objects, the DBMS must keep track of past trajectories. As time passes these trajectories continue to increase in length, and with large and often increasing number of moving objects, the database size can increase dramatically. Consequently, the backend DBMS must deploy scalable techniques to deal with increasing data sizes, and increasing number of mobile objects. The key focus of the COMET project is on developing efficient and scalable methods for querying on past, present, and future locations of moving objects, and on scalable trigger mechanism in this environment. The expected results of this project may have a strong impact on emerging notification-based applications, such as emergency response systems, in which critical data needs to be disseminated to a physical mobile user based on the user's current and changing spatial location. The project will also train a number of graduate and undergraduate students. The project Web site (http://www.eecs.umich.edu/~jignesh/comet) will be used for making the COMET software, all developed applications, and real user movement data freely available to a broad research community.