Motivation Modem enterprises rely on database management systems (DBMS) to collect, store and manage corporate data, which is considered a strategic corporate re source. Recently, with the proliferation of personal computers and departmen tal computing, the trend has been towards the decentralization and distribution of the computing infrastructure, with autonomy and responsibility for data now residing at the departmental and workgroup level of the organization. Users want their data delivered to their desktops, allowing them to incor porate data into their personal databases, spreadsheets, word processing doc uments, and most importantly, into their daily tasks and activities. They want to be able to share their information while retaining control over its access and distribution. There are also pressures from corporate leaders who wish to use information technology as a strategic resource in offering specialized value-added services to customers. Database technology is being used to manage the data associated with corporate processes and activities. Increasingly, the data being managed are not simply formatted tables in relational databases, but all types of ob jects, including unstructured text, images, audio, and video. Thus, the database management providers are being asked to extend the capabilities of DBMS to include object-relational models as well as full object-oriented database man agement systems.