A flexible approach to evolution of reconfigurable systems

In an evolving environment where unpredictable changes can occur, or where changes can occur at unpredictable times, it is essential to take a flexible approach to configuration management. The authors consider the provision of flexible methods for constraining unplanned evolution and for specifying programmed structural change. Reconfigurable systems can be divided into two categories: systems where the changes which can occur (and the conditions under which they can occur) must be declared at the time the system is designed, i.e. programmed change; and systems where the changes are specified at the time they are required-the time at which this happens may not be predictable, i.e. unplanned change. Management of evolving systems which are subject to (externally initiated) unplanned change is more difficult than for systems which internally initiate programmed change. For programmed change, a user simply identifies which change is required (or the system detects the conditions when the change is necessary). The system knows about the change and the management can be built in to the system. The authors describe a method of specifying structural constraints for a system and present a suitable method of specifying structural change