1. In a data processing system, a computer-implemented method for controlling access to a plurality of data objects, comprising the steps of: when each of the plurality of objects is created, associating with such object at least one user identifier, and at least one list of data manager identifiers; invoking a first data manager using a user identifier to identify an invoking user; invoking a second data manager from the first data manager; and when the second data manager later attempts to access a data object, allowing such access only if one of the lists of data manager identifiers associated with the data object contains both the first and second data managers, and the first data manager has been invoked with a user identifier associated with the object.