Title Semantics of Time - Varying Attributes and Their Use for TemporalDatabase DesignCopyright c 1997 Christian

This paper concerns the design of temporal relational database schemas. Normal forms play a central role during the design of conventional relational databases, and we have previously extended all existing relational normal forms to apply to temporal relations. However, these normal forms are all atemporal in nature and do not fully take into account the temporal semantics of the attributes of temporal relations. Consequently, additional guidelines for the design of temporal relations are required. This paper presents a systematic study of important aspects of the temporal semantics of attributes. One such aspect is the observation and update patterns of attributes|when an attribute changes value and when the changes are recorded in the database. A related aspect is when the attributes have values. A third aspect is the values themselves of attributes|how to derive a value for an attribute at any point in time from stored values. Guidelines for the design of the logical schema of a temporal database are introduced, and implications of the temporal-attribute semantics for the design of views and the physical schema are considered. The Bitemporal Conceptual Data Model, the data model of the consensus temporal query language TSQL2, serves as the context for the study.