Timeline Variability The Variability Of Binding Time Of Variation Points

E. Dolstra, G. Florijn and E. Visser. Timeline Variability: The Variability of Binding Time of Variation Points. In J. van Gurp and Jan Bosch, editors, Workshop on Software Variability Management (SVM'03), Groningen, The Netherlands, February 2003. (pdf)

Abstract

Timeline variability is the ability of a software system to have variation points bound at different moments of the system s life-cycle.

Virtually every non-trivial software system exhibits variability: the property that the set of features characteristics of the system that are relevant to some stakeholder can be changed at certain points in the system s life-cycle. The parts of the system that implement the ability to make such changes are called variation points. Selecting some variant supported by a variation point is called binding the variant. Every variation point has at least one associated binding time: the moment in the system s life-cycle at which the variation point can be bound. A more detailed exposition of this terminology can be found in, e.g., [7, 2]. Apache httpd webserver allows server extensions to be included at build time or at load time, but through different configuration mechanisms. Microsoft Office 2000 allows components to be installed either at install time proper or on demand, at runtime. The concept of timeline variability that is, variability of binding time should not be confused with the binding time of variation points. In this paper we illustrate timeline variability through two case studies, Apache and the Linux kernel, and show that the two main technical issues in timeline variability are inconsistent configuration interfaces and ad hoc implementation mechanisms. We also provide some directions for future research.