Variational lists: comparisons and design guidelines

Variation is widespread in software artifacts (data and programs) and in some cases, such as software product lines, is widely studied. In order to analyze, transform, or otherwise manipulate such variational software artifacts, one needs a suitable data structure representation that incorporate variation. However, relatively little work has focused on what effective representations could be to support programming with variational data. In this paper we explore how variational data can be represented and what the implications and requirements are for corresponding variational data structures. Due to the large design space, we begin by focusing on linked lists. We discuss different variational linked-list representations and their respective strengths and weaknesses. Based on our experience, we identify some general design principles and techniques that can help with the development of other variational data structures that are needed to make variational programming practical.