Attention to the temporal aspects of data management has intensified in recent years,focusing on data models and related systems that are sensitive to the ubiquitous temporal aspects of data. Both the growing need for easier access to historical data, as well as the imminent availability of mass storage devices, are makingthis apromisingbranchof database research, both practically and theoretically. In this paper we summarize the main results of recent research on temporally sensitive data models, discuss the lessons learned in their development, and assess the prospects and dimculties involved in incorporating a temporal dimension into database management systems (TODBs). Inparticular, three system levels are identified: the external userview of the database; an intermediate view closer to the structure of an existing data model; and an internal or implementation view defined interms of low level data structures. This general architecture coherently incorporates a variety of related research results and development experiences, and serves as the framework for theoretical and implementation research into such systems