【摘要】 <正> 1 引言近年来,Internet/Web技术和计算机硬件的迅速发展对数据库研究领域产生了巨大的影响,提出了新的挑战性问题:一是如何使数据库系统和技术成为Web的有机组成部分,而不仅仅充当Web体系的外围角色;二是如何实现Web动态信息的管理,完成日益增多的新一代Web应用等。人们已认识到Web正在逐渐成为全球性的自主分布式计算环境,Web上的多数站点都具有丰富的数据资源。如果能够把遍及全球的Web数据源集成起来,Web将成为一个全球统一的数据库,由全世界共享。然而Web数据源的集成并非易事,数据源的异构问题是影响Web数据源集成的最大障碍。Web数据源的异构问题主要包括三个方面:第一是模式异构,表现在不更多还原

【Abstract】 As the Web comes to be viewed as a large semistructured database with XML as its model, issues related to querying semistructured data in general, and XML in particular, become more important. In this paper, based on the MIX and W4F,a system of integrating and accessing heterogeneous data sources is presented. The system accesses a set of XML sources, which are currently information systems wrapped to provide (1) an XML view of their data and (2) a set of XMAS queries that they can answer. Conceptually, it exports an integrated view of the source data. The view definition, provided by the view developer, specifies how the source data will be integrated. Especially, the wrapper for Web data sources is generated by the W4F and the system does not materialize the integrated view in ad.更多还原