Object-bases are certain to supplant today's file systems in future program development environments. Unfortunately, file systems implicitly provide several important environmental features that are difficult or impossible to obtain using existing object-bases, such as focus of attention, garbage detection and collection, and data sharing. These deficiencies arise from the absence of mechanisms for naming and maintaining aggregations of information in structures larger than single relations or single object classes. This paper proposes a model for information in programming environments, called worlds, which naturally describes clusters of information forming conceptual units in an object-base. Because the model arose from the need to represent well-formed grammatical structures, the concept unifies syntax-directed manipulation with object-base facilities. In addition, this clustering capability provides a foundation in object-bases for the features lost from file systems. We illustrate worlds through their use to maintain persistence in the object-base of our programming environment, the Common Lisp Framework.