Most object-oriented databases can only be accessed by a programming language rather than a query language, although an ad hoc query facility is a desirable feature of such systems. In this paper, we present a way to process queries to extract data from a collection of interacting objects. We adopt the object-oriented paradigm to describe the operational semantics of queries given as expressions of a query algebra. An expression can be transformed into a collection of active objects performing the operations. We show that we are able to implement query processing using the existing framework for collections of objects, which is based on objects modeled as processes. Our approach makes parallel query processing possible