Temporal entity-relationship models-a survey
IEEE Transactions on Knowledge and Data Engineering
Any software made available via TimeCenter is provided \as is" and without any express or implied warranties, including, without limitation, the implied warranty of merchantability and tness for a particular purpose. The TimeCenter icon on the cover combines two \arrows." These \arrows" are letters in the socalled Rune alphabet used one millennium ago by the Vikings, as well as by their precedessors and successors, The Rune alphabet (second phase) has 16 letters. They all have angular shapes
... e angular shapes and lack horizontal lines because the primary storage medium was wood. However, runes may also befound on jewelry, tools, and weapons. Runes were perceived by many a s h a ving magic, hidden powers. The two Rune arrows in the icon denote \T" and \C," respectively. Abstract The Entity-Relationship (ER) Model, using varying notations and with some semantic variations, is enjoying a remarkable, and increasing, popularity in both the research community, the computer science curriculum, and in industry. In step with the increasing di usion of relational platforms, ER modeling is growing in popularity. It has been widely recognized that temporal aspects of database schemas are prevalent and di cult to model using the ER model. As a result, how to enable the ER model to properly capture time-varying information has for a decade and a half been an active area of the database research community. This has led to the proposal of almost a dozen temporally enhanced ER models. This paper surveys all temporally enhanced ER models known to the authors. It is the rst paper to provide a comprehensive o verview of temporal ER modeling, and it thus meets a need for consolidating and providing easy access to the research in temporal ER modeling. In the presentation of each m o d e l , the paper examines how t h e time-varying information is captured in the model and present the new concepts and modeling constructs of the model. A total of 20 di erent design properties for temporally enhanced ER models are de ned, and each model is characterized according the these properties 1 .