  Distributed architectures have become ubiquitous in many complex technical
and socio-technical systems because of their role in improving uncertainty
management, accommodating multiple stakeholders, and increasing scalability and
evolvability. This departure from monolithic architectures provides a system
with more flexibility and robustness in response to uncertainties that it may
confront during its lifetime. Distributed architecture does not provide
benefits only, as it can increase cost and complexity of the system and result
in potential instabilities. The mechanisms behind this trade-off, however, are
analogous to those of the widely-studied transition from integrated to modular
architectures. In this paper, we use a conceptual decision framework that
unifies modularity and distributed architecture on a five-stage systems
architecture spectrum. We add an extensive computational layer to the framework
and explain how this can enhance decision making about the level of modularity
of the architecture. We then apply it to a simplified demonstration of the
Defense Advanced Research Projects Agency (DARPA) fractionated satellite
program. Through simulation, we calculate the net value that is gained (or
lost) by migrating from a monolithic architecture to a distributed architecture
and show how this value changes as a function of uncertainties in the
environment and various system parameters. Additionally, we use Value at Risk
as a measure for the risk of losing the value of distributed architecture,
given its inherent uncertainty.
