Evolution of Persistent Types

Persistent type evolution is a problem specific to the modification of types used to define persistent objects. In languages that support object persistence directly, such as Java, the storage representation used for persistent objects is derived directly from the object's type representation. If a programmer modifies the structure of a persistent type, that modification affects both its representation in virtual memory and its representation in a persistent object base. If an object is written to an object base, and then the type representation used by that object is changed, it may no longer be possible to read the object from the persistent object base. My research addresses four broad problems of persistent type evolution:

How can a system identify the changes a programmer makes to a collection of types?
After understanding the type changes, how can a system generate a transformer that will update the persistent objects to comply with the changed types?
What are the limits of automated transformer generation and how can the system support programmer-defined extensions to the generated transformer?
What mechanisms support transformation of persistent objects in the most efficient and least obtrusive manner?

The following papers are available:

Barbara Staudt Lerner, "TESS: Automated Support for the Evolution of Persistent Types", in Proceedings of the 1997 Automated Software Engineering Conference (ASE'97), November 1997.: Abstract; Paper
Barbara Staudt Lerner, A Model for Compound Type Changes Encountered in Schema Evolution, Technical Report 96-044, Computer Science Department, University of Massachusetts at Amherst, June 1996.: To ftp the report, click UM-CS-1996-044
Barbara Staudt Lerner, Type Evolution Support for Complex Type Changes, Technical Report 94-071, Computer Science Department, University of Massachusetts at Amherst, 1994.: To ftp the report, click UM-CS-1994-071

This work was supported in part by the Air Force Materiel Command, Rome Laboratory, and the Defense Advanced Research Projects Agency and in part by the National Science Foundation.