Persistence in the Spring system

The Spring1 system does not provide persistent object identifiers and not all Spring objects are persistent. Instead, we rely on a general name service and persistent name-to-object bindings to support persistence. The name service is separate from the various subsystems that imple- ment persistent objects, so that new object types can be added, and the implementation of existing types can be changed, without rebuilding the name service. We distinguish among the concepts of freezing, pickling, and externalizing. We then develop a general framework for freezing that can be used by any client, including the name server, for making objects persistent. It allows sub- systems that implement objects of various types to maintain autonomy from the name service and retain control over how their objects are implemented and made persistent, and yet be well integrated with the name service.