The System Shell As A Construct for Mitigating the Impact of Changing Contexts by Creating Opportunities for Value Robustness

One of the primary goals in developing systems is to create a system that delivers desired capabilities, or value, to system stakeholders. In practice, system development requires both creative design for meeting the system objectives on paper, as well as technical competence to ensure system value delivery in practice. At least several failure mechanisms exist that may prevent a system from delivering value in practice. These mechanisms include poor concept design, failure in design implementation, changes in system operating context, and changes in stakeholder expectations. Whereas traditional robust design deals with changes in operating context, designing for Value Robustness is a technique to ensure value delivery in spite of changes in a more generalized context and expectations. The concept of system shell is introduced as a value robust construct for mitigating the effect of changes in context and expectations by decoupling the system from the sources of change. The system shell consists of two parts: the system mask and the system shelter. The system mask changes how the system is "seen" by the external context and stakeholders. The system shelter changes how the system "sees" its external context and stakeholders. Examples of system shell applications are presented, as implemented in both software and hardware, and across applications from consumer products to aerospace systems. Implications for the design of systems and systems of systems are discussed, including customizing perception of value delivery, integrating legacy components, and balancing changeability with robustness. Given uncertainty in future system context and use, the purposeful addition of system shells as a part of system design is proposed as a cost-effective approach to maintaining system value in spite of changes in context and stakeholder expectations.