Managing Conflicting Requirements in Systems of Systems by Adaptation

A System of Systems (SoS) is an arrangement of useful and independent complex systems, which are integrated into a bigger system that delivers unique capabilities [1]. In this context, it is important to notice that each independent system should be capable of operate and fulfil useful purposes on its own environment, but, when these independent systems are together and become a SoS they are able to achieve new objectives that could not be achieved by the individual systems. This means that, while at the same time achieving key quality objectives such as performance, reliability or security, a SoS can offer more functionality than the sum of the constituent systems [2]. However, as the SoS is formed by the integration of independent complex systems, this will increase the complexity of the SoS to, at least, one more order than its component systems [3]. This means that problems in the SoS environment are harder to handle than in the component system environment. A common problem that is present into all types of systems is the conflicting requirements. Due to voluminous requirements documents, constant changes into requirements, complexity and presence of different stakeholders, conflicts arise within each component system and also across the SoS due to unexpected interactions between components, users and SoS goals [4]. In the SoS environment, there are different component systems that often came from different domains, developed by different teams, under different circumstance and time. Also, each component system evolves into a different rhythm. Therefore, the SoS environment is even more likely to present and be affected by conflicting requirements. Actually, there are approaches to handle with conflicting requirements, however, no one of them takes into account the differences present in the SoS environment: the independence of each component system, the increased order of complexity, the distributed nature and the dynamic and flexible boundaries. On the other hand, adaptation is way to support a system and help it to modify their behaviour and structure in response to their perception of the environment [5]. Moreover, the SoS is known to be adaptive by nature [6]. Thus, this research aims to propose a way to support the SoS in its task to manage conflicting requirements by adaptation. II. CONFLICTING REQUIREMENTS