A processing framework for object comprehensions

In order to execute database queries eeciently, they are usually translated into an algebra: a small set of operations together with some equivalences. The operations are implemented very eeciently by the database engine, and the equivalences are used to optimise the query. Since query languages for object-oriented databases are more complex than their relational counterparts , the algebra and translation, or processing framework, is more elaborate. This paper describes the processing framework for object comprehensions , a powerful object-oriented query language. Both operations and equivalences of the algebra are deened, together with a translation into it. The framework is illustrated by translating and optimising an example object comprehension query.