Requirements Evolution and Evolution Requirements with Constrained Goal Models

We are interested in supporting software evolution caused by changing requirements and/or changes in the operational environment of a software system. For example, users of a system may want new functionality or performance enhancements to cope with growing user population (changing requirements). Alternatively, vendors of a system may want to minimize costs in implementing requirements changes (evolution requirements). We propose to use Constrained Goal Models (CGMs) to represent the requirements of a system, and capture requirements changes in terms of incremental operations on a goal model. Evolution requirements are then represented as optimization goals that minimize implementation costs or customer value. We can then exploit reasoning techniques to derive optimal new specifications for an evolving software system. CGMs offer an expressive language for modelling goals that comes with scalable solvers that can solve hybrid constraint and optimization problems using a combination of Satisfiability Modulo Theories (SMT) and Optimization Modulo Theories (OMT) techniques. We evaluate our proposal by modeling and reasoning with a goal model for the meeting scheduling examplar.