Managing change in persistent object systems

Abstract

Persistent object systems are highly-valued technology because they offer an effective foundation for building very long-lived persistent application systems (PAS). The technology becomes more effective as it offers a more consistently integrated computational context. For it to be feasible to design and construct a PAS it must be possible to incrementally add program and data to the existing collection. For a PAS to endure it must offer flexibility: a capacity to evolve 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 effectively. 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 identifies change absorbers as a means of describing how changes should propagate. It is argued that if we systematically develop an adequate repertoire of change absorbers then they will facilitate much better quality change management.