We present a functional paradigm for querying efficiently abstract collections of complex objects. Abstract collections are used to model class extents, multivalued attributes as well as indexes or hashing tables. Our paradigm includes a functional language called OFL (Object Functional Language) and a supporting execution model based on graph traversals. OFL is able to support any complex object algebra with recursion as macros. It is an appropriate target language for OQL-like query compilers. The execution model provides various strategies including set-oriented and pipelined traversals. OFL has been implemented on top of an object manager. Measures of a typical query extracted from a geographical benchmark show the value of hybrid strategies integrating pipelined and set-oriented evaluations. They also show the potential of function result memorization, a typical optimization approach known as "Memoization" 2 in functional languages.