The generation of execution plans for object-oriented database queries is a new and challenging area of study. Unlike relational algebra, a common set of object algebra operators has not been defined. Similarly, a standardized object manager interface analogous to the storage manager interface of relational subsystems does not exist. We define the interface to an object manager whose operations are the executable elements of query execution plans. Parameters to the object manager interface are streams of tuples of object identifiers. The object manager can apply methods and simple predicates to the objects identified in a tuple. Two algorithms for generating such execution plans for queries expressed in an object algebra are presented. The first algorithm runs quickly but may produce inefficient plans. The second algorithm enumerates all possible execution plans and presents them in an efficient, compact representation.>

Object-oriented database mangement systems (OODBMS) combine the data abstraction and computational models of object-oriented programming languages with the query and performance capabilities of database management systems. A concise, formal data model for OODBMS has not been universally accepted, preventing detailed investigation of various system issues such as query processing. We define a data model that captures the essence of classification-based object-oriented systems and formalize concepts such as object identity, inheritence, and methods. The main topic of the paper is the presentation of a query processing methodology complete with an object calculus to object algebra translation are discussed in detail. The paper concludes with a discussion of equivalence-preserving transformation rules for object algebra expressions.