The Kbo Model: Towards A Unified View Of Data, Behaviors, And Messages In Object-oriented Database Systems

One of the most distinguished features of object-oriented databases (OODBs) is their support for users to populate both data and arbitrary behaviors in the same database. Consequently, the increasingly large population of arbitrary behaviors in OODBs demands a database approach to their management and manipulation. Current OODB models offer no capability of managing arbitrary behaviors as meaningful database objects, and thus fail to meet such a demand.;The goal of this research is to unify data, behaviors, and messages into a uniform notion of objects so that a single database approach can be developed to manage and manipulate such objects. The result is a formal object-oriented data model, the KBO model, which integrates data, arbitrary behaviors, and messages into a more general notion called Knowhow-Bearing-Objects --objects that always bear an executable reference called knowhow . Management of such objects is characterized by the mechanisms developed in six coherently related aspects: classification, re-utilization, identification, invocation, composition, and manipulation.;Classification of KBO objects is based on value structures, rather than on signatures or source code. Classes are related through two independent hierarchies: the KIND-OF hierarchy and the REUSE-OF hierarchy. A formal semantics is defined for the two hierarchies and theorems are developed to provide formal mechanisms for their syntactic validation. Identification of KBO objects is based on identities rather than on executable references. Invocation of KBO objects using both identities and values as behavior selectors comes naturally, thus providing the support for both monomorphism and polymorphism. Composition of KBO objects is based on four generic object structures which also imply dynamic semantics. As a result, complex objects can be directly used as complex messages to invoke complex behaviors. Theorems are developed to provide formal mechanisms to ensure the safety and success of complex messages. Manipulation of KBO objects is based on an object algebra, the KBO algebra, which can be used, not only to manipulate traditional data, but also to select, generate, maintain, and apply behaviors, in an associative manner. The properties of the algebra are formally analyzed, and theorems are developed to provide provably correct algebraic transformations