Browse Theses

In this thesis a new data model called FERM (Functional Entity Relationship Model) is introduced in order to improve the semantic modeling capability of database systems. FERM is an integration and extension of the Functional Data Model and the Entity Relationship Model. FERM consists of a small number of primitive elements such as entity sets, attribute types, and database storage functions together with a set of integrity constraints called domain-range constraints. Functional relationships between entities and attributes of an entity are represented in FERM by database storage functions. High-level semantics such as ISA relationships, existence dependencies, mandatory relationships, case and disjointness relationships are all expressed in FERM in terms of domain-range constraints on database storage functions. Thus, consistent database storage states with respect to such high-level semantics can be studied by analyzing the effect of database update operations on domain-range constraints.

This thesis gives a formal definition of FERM including update (insertion, deletion, replacement) operations. This remedies two major shortcomings of previous work in the Functional and Entity Relationship Model area: (1) the lack of a formal definition; (2) the absence of update operations in these models.

A major emphasis in this thesis is placed upon the study of correct update operations. A major contribution is the introduction of a finite set of update operations called unit update operations which have three important properties: (1) they are all consistent (i.e., correct) transactions with respect to a given set of domain-range constraints; (2) they are minimal in the sense that no unit update operation can be simplified any further without becoming incorrect, and (3) all other consistent transactions can be constructed from unit update operations using a given set of correctness-preserving constructors (completeness property). An algorithm for generating a complete and minimal set of unit operations is given and correctness of this algorithm is proven.

These results may be used as a basis for the development of a FERM database design methodology. The Database Administrator can construct user-level correct transactions by composing unit operations generated automatically. This approach may ultimately result in improved productivity and reliability of database application development.