A compliant persistent architecture
Ron Morrison, Dharini Balasubramaniam, Mark Greenwood, Graham Kirby, Kenneth R. Mayes, Dave Munro, Brian Warboys · Software Practice and Experience · 2000
The changing needs of modern application systems demand new and radical software architectures to support them. The attraction of persistent systems is that they define precisely the extent to which they are open, thereby allowing the dynamically changing resource requirements of applications to be tracked accurately within the persistent environment. Thus, an ever-growing body of work is being established to study the nature of running applications, and to use the information gleaned, to improve the run-time execution of these applications. Here we propose a new architectural approach to constructing persistent systems that accommodates, and thus is compliant to, the needs of particular applications. By separating policy from mechanism in all components, the architecture may be tailored to the policy needs of the application. (Policy may be regarded as strategy for achieving a goal, such as a cache eviction algorithm, whereas mechanism is the method by which the objective is achieved, such as the physical movement of the cache lines. As we see later, policy and mechanism are composable to form new mechanism.) We first propose a generic architecture for compliance, and then show how it may be instantiated. Finally, we describe an example of how the architecture operates in a manner that is compliant to a target application. We postulate, since we have not yet measured, that the benefits of compliant architectures will be a reduction in complexity, with corresponding gains in flexibility, portability, understandability in terms of failure semantics, and performance. Copyright © 2000 John Wiley & Sons, Ltd.