Challenges in the modelling of SoS design alternatives with MBSE

A central promise of Model-Based Systems Engineering (MBSE) is to decrease the volume of information produced during the system design lifecycle through improved structure and smarter reuse across the numerous perspectives and architectural levels. The study of variants is a core challenge within MBSE due to associated exponential information growth, and the complexity created by this extra dimensionality. Variant management has been discussed extensively for the physical layer, but lacks research focusing on functional and logical layers, particularly relevant to concept phase engineering. In System of Systems (SoS) problems, the physical choices are typically constrained by the fact that the interacting systems already exist. This paper therefore studies the implications of variant modelling for the behaviour of the SoS. It explores the possibility of developing a functional architecture that can be extended to accommodate changes due to decisions made in the logical layer. It investigates the formal aspects of including variant modelling into the Systems Modelling Language (SysML) and discusses the potential need for a language extension.