Heidi Gregersen

Temporal entity-relationship models-a survey

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 diffusion of relational platforms, ER modeling is growing in popularity. It has been widely recognized that temporal aspects of database schemas are prevalent and difficult 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 in the database research community. This has led to the proposal of close to a dozen temporally enhanced ER models. This paper surveys all temporally enhanced ER models known to the authors. It provides a comprehensive overview 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 model, the paper examines how the time-varying information is captured in the model and presents the new concepts and modeling constructs of the model. A total of 19 different design properties for temporally enhanced ER models are defined, and each model is characterized according to these properties.

On the Ontological Expressiveness of Temporal Extensions to the Entity-Relationship Model

It is widely recognized that temporal aspects of database schemas are prevalent, but also difficult to capture using the ER model. The database research communitys response has been to develop temporally enhanced ER models. However, these models have not been subjected to systematic evaluation. In contrast, the evaluation of modeling methodologies for information systems development is a very active area of research in the information systems engineering community. Based on a framework from information systems engineering, this paper evaluates the ontological expressiveness of three different temporal enhancements to the ER model. The three temporal ER model extensions are well-documented, and together the models represent a substantial range of the design space for temporal ER extensions.