CHiSEL: a user-oriented framework for simplifing database evolution

In order to conduct research effectively, scientists must be able to access, organize, describe, and produce data as part of their daily research activities. While relational databases are well suited to the tasks of describing and organizing scientific metadata and results, the difficulties of using relational database management systems effectively, have resulted in their limited adoption among scientists. In addition, scientific research is changing steadily with new experimental protocols, instruments, and discoveries that determine what data are generated and how they must be described and organized according to a relational schema. Unfortunately, evolving a schema is one of the most difficult aspects of database usage. The conventional data definition and manipulation languages offer relatively low-level programming abstractions to perform complex database evolution tasks, and therefore require specialized technical skills not possessed by most scientists. A simplified means of expressing database evolution operations would reduce the effort for non-expert users of databases. This paper presents a high-level, user-oriented, schema evolution framework built on a formal algebra of schema modification operators. The approach allows introduction of novel operators as motivated by new requirements and is amenable to well established optimization techniques for efficient planning and execution. We also propose a rigorous evaluation methodology for comparing the user effort of database evolution languages, and we introduce a benchmark for evaluating the execution efficiency of schema evolution expressions. We present the framework and its implementation, and we demonstrate its utility in exemplar use cases and a performance evaluation.