ObjectStore in an object-oriented database system supporting persistence orthogonal to type, transaction management, and associative queries. collections are provided as objects. the data model is non-INF, as objects may have embedded collections. queries are integrated with the host language in the from of query operators whose operands are a collection and a predicate. the predicate may itself contain a (nested) query operating on an embedded collection. indexes on paths may be added and removed dynamically. collection, being treated as objects, may be referred to indirectly, e.g. through a by-reference argument. for this reason and others, multiple execution strategies are generated, and a final selection is made just prior to query execution. nested queries can result in interleaved execution and strategy selection.