Examining Survivability of Systems of Systems

Previous research has identified design principles that enable survivability for systems, but it is unclear if these principles are appropriate and sufficient for systems of systems as well. This paper presents a preliminary examination of how some of the characteristic properties of systems of systems may enable or hinder survivability, based on existing design principles and a newly proposed taxonomy of disturbances. Two new design principles, defensive posture and adaptation, are introduced. The next phase of research will be to conduct empirical studies to validate the design principles against some of the characteristic properties of systems of systems, and test hypotheses about how survivability will be affected. In troduction As systems complexity grows, traditional systems are being interconnected to form larger, more capable systems of systems (SoS). In many circumstances, systems of systems are operated in contexts that are subject to disturbances which may impact the ability of the SoS to deliver value. Increasing the survivability of systems can be expensive, and typically involves trade offs. Decision makers are forced to select options that balance value, cost and risk according to their needs, but in systems of systems, the problem is often compounded due to diverse stakeholders and conflicting risk mitigation strategies (Ellison and Woody 2007). Systems engineering design principles to aid designing systems for enhanced survivability were developed in a previous research effort (Richards 2009), but the case studies upon which they were developed and validated, involved traditional systems, such as satellite radar. There has been some debate as to whether traditional systems engineering methods and practices are still valid at the SoS level (Dicke rson 2009) . The literature is unclear as to the definition of a SoS, and how it is distinct from a traditional system (Chattopadhyay 2008). This is not surprising, since the definitions of a "system" itself is also ambiguous (Backlund 2000). However, systems of systems can be thought of as a special case of systems, and thus it is important to highlight the characteristic properties of a SoS, and determine how they might affect its survivability. Unfortunately, the concept of survivability upon which the original design principles were generated, was based upon a definition of disturbances that was insufficient for many of the types of problems a SoS may face. Since systems of systems tend to be larger, more complex and operate under more varied contexts than traditional systems, a broader definition of disturbances is needed. This paper has two goals; (1) To point out deficiencies in the existing classification of disturbances and propose a new taxonomy, and (2) generate hypotheses as to whether or not some of the characteristic properties of systems of systems affect its survivability. The paper begins with the existing definition of survivability and original design principles that enable it for systems.