Extending Temporally ER Model for Designing Temporal Databases with Multiple Time Granularities
Entity-Relation (ER) model may be used for different but related purposes, e.g. to model real world for analysis, to describe a database scheme of a computer system for design. In recent years, with the increasing needs of time-related application, how to extend the ER model to enable it to properly capture time-varying information has been active area of research. By extending temporally traditional ER models, the authors propose a new temporal ER model, which is called ETER model. For the ETER model, they introduce two new constructs including variety granularity and time cardinality. They discuss how to specify time-varying attributes and relationships using these constructs, and how to specify TFDs constraints.