The Requirements Problem for Adaptive Systems

Requirements Engineering (RE) focuses on eliciting, modeling, and analyzing the requirements and environment of a system-to-be in order to design its specification. The design of the specification, known as the Requirements Problem (RP), is a complex problem-solving task because it involves, for each new system, the discovery and exploration of, and decision making in a new problem space. A system is adaptive if it can detect deviations between its runtime behavior and its requirements, specifically situations where its behavior violates one or more of its requirements. Given such a deviation, an Adaptive System uses feedback mechanisms to analyze these changes and decide, with or without human intervention, how to adjust its behavior as a result. We are interested in defining the Requirements Problem for Adaptive Systems (RPAS). In our case, we are looking for a configurable specification such that whenever requirements fail to be fulfilled, the system can go through a series of adaptations that change its configuration and eventually restore fulfilment of the requirements. From a theoretical perspective, this article formally shows the fundamental differences between standard RE (notably Zave and Jackson [1997]) and RE for Adaptive Systems (see the seminal work by Fickas and Feather [1995], to Letier and van Lamsweerde [2004], and up to Whittle et al. [2010]). The main contribution of this article is to introduce the RPAS as a new RP class that is specific to Adaptive Systems. We relate the RPAS to RE research on the relaxation of requirements, the evaluation of their partial satisfaction, and the monitoring and control of requirements, all topics of particular interest in research on adaptive systems [de Lemos et al. 2013]. From an engineering perspective, we define a proto-framework for solving RPAS, which illustrates features needed in future frameworks for adaptive software systems.