Algebraic transformation and optimization techniques have been the method of choice in relational query execution, but applying them in OODBMS has been difficult due to the complexity of object-oriented query languages. This paper demonstrates that the problem can be simplified by mapping a complex storage model to the flat binary model implemented by Monet, a state-of-theart database kernel. We present a generic mapping scheme to flatten data models and study the case of a straightforward object-oriented model. We show how flattening enabled us to implement a full-fledged query algebra on it, using only a very limited set of simple operations. The required primitives and query execution strategies are discussed, and their performance is evaluated on the 1GB TPC-D benchmark, showing that our divide-and-conquer approach yields excellent results. 1 Introduction During the last decade, relational database technology has grown towards industrial maturity, and the attention of the research...