In database or knowledge-base systems, query formulation languages are the means offered to users for accessing data or knowledge. Queries allow selection of data under particular, either simple or complex constraints, resulting from one or several structures. However, query formulation remains obstinately difficult for large classes of users. Indeed, with the exception of approaches facilitating syntax problems, there is a noticeable absence of models taking charge of the user through specification of their needs to formulation of their queries. In the case of object-oriented database systems, whose data models and concepts are more complex than those of relational databases, database users need assistance with several kinds of formulation problems. In this respect, we consider that the storage and reuse of former queries constitutes a promising avenue of investigation. We take a novel look at object-oriented queries, reifying the ones which users formulate as components then reusing them, by means of strategies for selecting, assembling and adapting them to help in the formulation of new complex queries