Managing Change in Persistent Object Systems

Persistent object systems are highly-valued technology because they ooer an eeec-tive foundation for building very long-lived persistent application systems PAS. The technology becomes more eeective as it ooers a more consistently integrated computational context. For it to be feasible to design and construct a PAS it must be possible to in-crementally add program and data to the existing collection. Fo r a P AS to endure it must ooer exibility: a capacity t o e v olve and change. This paper examines the capacity of persistent object systems to accommodate incremental construction and change. Established store based technologies can support incremental construction but methodologies are needed to deploy them eeectively. Evolving data description is one motivation for inheritance but inheritance alone is not enough to support change management. The case for supporting incremental change is very persuasive. The challenge is to provide technologies that will facilitate it and methodologies that will organise it. This paper identiies change absorbers as a means of describing how c hanges should propagate. It is argued that if we systematically develop an adequate repertoire of change absorbers then they will facilitate much better quality c hange management .