Treffer: A FORMAL MODEL OF ODS SCHEMA IN LIPS.

LIPS (Library Information Processing System) which I have proposed during the study for my research. A library system contains books, authors, and users and many types of other materials. The Location in identified for books by a Class Number, authors by authors name, and user by a user name. To execute a query on any of these components the Management Software needs accumulated expression, formulae and rules. Therefore, semantics of an Object Oriented Database System schema greatly depends on the model theory of accumulated expression calculus. Moreover, an ODS schema involves recursive specification. Recursion arises with recursive rules as well as with recursive message definition. In order to uniquely define the semantics of such a schema the structure of models plays an important role. It has been shown during this discussion that for a restricted class of schema, the semantics can be uniquely specified. The intention of this article is to highlight the finding during our study on LIPS regarding the used expression, formulae and rules in the ODS schema. The approach used here is the least fixed-point approach of specification of semantics. In the following discussion we exclude formulae, which involves negation. Unless explicitly mentioned a formula is assumed to be free of negation. The utility of different features of algebra will be clear in subsequent sections when the tools developed here are used in describing the semantics for query processing. [ABSTRACT FROM AUTHOR]