Date of Award
Doctor of Philosophy
Shashi K. Gadia
Arthur E. Oldehoeft
A temporal relational database model that supports queries on updates and errors is obtained by attaching 2-dimensional timestamps to data values. The two time dimensions represent real world time, the time when events take place in the real world, and transaction time, the time when such events are recorded in the database. A timestamp in our model is a temporal element, which is a finite union of temporal intervals, or rectangles. The resulting 2-dimensional temporal model includes a robust concept of keys. The concept of keys is essential for restructuring formless temporal information in weak relations;This model does not preclude the possibility that key values may sometimes by recorded in error. Therefore, among its update operations is one that allows changes in key attribute values. Since key values can change to accommodate previous errors, a mechanism to store the "true" identity of objects is provided. This is done through anchors;Relations in the 2-dimensional model can "store" the results of all updates. This obviates the need for an explicit update log. Not only that, since updates are now part of the relational structure, constructs of the relational algebra can be used to query their nature. The algebra for the model includes powerful, yet simple, primitives for querying for updates and errors;The zero information-loss model uses the basic 2-dimensional model to provide complete information recoverability. The effect of all database transactions and their circumstances is "stored" in the model. As a result, there is no longer any need for explicit transaction logs. In the zero information-loss model it is possible to have queries on queries, queries on queries on queries, ad infinitum. This model is a promising framework for building secure and auditable database systems.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Bhargava, Gautam, "A 2-dimensional temporal relational database model for querying errors and updates, and for achieving zero information-loss " (1989). Retrospective Theses and Dissertations. 9104.