| Managing the variability in software systems is rapidly becoming an important factor in software development. Instead of developing and deploying a fixed one-of-a-kind system, it is now common to develop a family of systems whose members differ with respect to functionality or technical facilities offered. Variability is represented conceptually by variation points that identify a set of variants for which a choice or decision can be made at a particular moment - binding time - in the development and deployment cycle of a software system. Depending on the needs of the system's stakeholders, it may be desirable to allow these decisions to be made at several moments in time. This timeline variability is an extra dimension to variability that is often ignored. Variability decisions are realized via configuration mechanisms, which are closely tied to specific moments in the deployment cycle. As a result, the variability in a system is mostly not orthogonal to the timeline, and often appears to have been designed in an ad-hoc fashion. Providing several moments at which a decision can be made is particularly hard to implement and thus seldom provided. Also, the collection of mechanisms often leads to a complex configuration interface. The goal of this project is to study the modeling and realization of variability in modern software systems with an emphasis on a more general and generic treatment of timing issues for variant addition/removal and binding of variation points, the related effects and the opportunities for optimization. The vehicle for the research is the development of a framework for transparent configuration environments which present a uniform interface to a variety of underlying configuration mechanisms, thus closing the current gap between variability at the conceptual and implementation levels. The realization of such environments requires: - models of variability that explicitly include timing issues and can cope with timeline variability; - component composition mechanisms that include composition of variability in components; - component integration mechanisms that cater for optimization of compositions; and - methods and techniques for variability discovery in existing systems. New in this project is the focus on timeline variability and the integrated treatment of variability spanning several areas including configuration management, language technology, and software reuse. The approach we take is application driven - drawing inspiration from and validating ideas against existing software - and tool-oriented - developing tools to support transparent specification and realization of timeline variability. |
