In the near future, large, complex, time-critical missions, such as disaster relief, will likely require multiple unmanned vehicle (UV) operators, each controlling multiple vehicles, to combine their efforts as a team. However, is the effort of the team equal to the sum of the operator's individual efforts? To help answer this question, a discrete event simulation model of a team of human operators, each performing supervisory control of multiple unmanned vehicles, was developed. The model consists of exogenous and internal inputs, operator servers, and a task allocation mechanism that disseminates events to the operators according to the team structure and state of the system. To generate the data necessary for model building and validation, an experimental test-bed was developed where teams of three operators controlled multiple UVs by using a simulated ground control station software interface. The team structure and interarrival time of exogenous events were both varied in a 2x2 full factorial design to gather data on the impact on system performance that occurs as a result of changing both exogenous and internal inputs. From the data that was gathered, the model was able to replicate the empirical results within a 95% confidence interval for all four treatments, however more empirical data is needed to build confidence in the model's predictive ability.

Abstract-Disturbances and disruptions, both internal and external to the system, are a major concern for system architects who are responsible for ensuring that their systems maintain value robustness no matter what occurs. These perturbations can have multiple causes and can affect a system in multiple ways. This paper presents a taxonomy of disturbances and disruptions to assist system architects and researchers in identifying the ways in which systems can fail to deliver value. By doing so, this taxonomy falls into a larger research effort to develop survivability design principles that will help system architects design systems that prevent, mitigate and recover from disturbances.

Abstract. 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.

Abstract-As systems become more complex, and have longer lifespans, they will likely encounter contextual variation or be themselves subject to change. Systems need to not only be feasible, but viable as well. That is, they need to be able to continue to provide value in spite of any potential exogenous or endogenous changes. Viability has been defined for other domains, but it has not been defined for engineered systems. This paper defines what it means for an engineered system to be viable, and shows that it is related to, but different from other existing "-ilities" such as survivability and reliability. This paper also addresses the need to ensure that endogenous changes do not inadvertently cause unintended interactions that harm the system overall. A new "-ility", pliability, is introduced that specifies the limits on how a system can change, without "breaking" or violating an architecture that was intended and validated. Like changeability, pliability increases robustness by allowing systems to voluntarily change in response to dynamic contexts, and increases survivability by increasing the likelihood that unintentional changes are still within the set of allowable architecture-defined instances. It also distinguishes allowable changes from those that would require additional validation, reducing the effort required to get those changes approved by a diverse set of stakeholders.

The concept of operations is often assumed when assessing different design variables in a tradespace study for a particular system architecture, The way a system operates, however, has a large effect on its performance, and can often be the only variable through which stakeholders can influence a system after the system is implemented. The concept of pliable system architectures is introduced so that operational variables can be explicitly considered and incorporated into tradespace studies. System transitions can be predicted by pliability, and these transitions can provide insight into other system "ilities" such as changeability, adaptability, flexibility and survivability. Two techniques are introduced in order to demonstrate the usefulness of the pliability concept; (1) a step-by-step process by which operational variables can be identified within a system architecture, and (2) a process by which very large tradespaces can be sampled into a manageable set of system instances that provide maximum insight for the level of effort to model them. As these new concepts and methodologies are new and part of ongoing research, they will need to be tested and validated in future work.