MOSA Reference Frameworks in Defense Acquisition Programs
2
1 Introduction
The Department of Defense (DoD) has employed modular open systems approaches (MOSA) for
nearly 20 years, but recent legislation (P.L. 114-328 2017) has formally mandated the use of
MOSA to enhance the Department’s ability to modify major weapon systems efficiently.
Modularization simplifies system design by making complexity manageable, enables programs to
conduct parallel development efforts, and accommodates future uncertainty by allowing for
incremental changes to a system (Baldwin 2006).
Successful MOSA implementations have proved that proper application of modular approaches
and flexible, open-system architectures allow for system components to evolve to respond to
changing “technology, threat, or interoperability need” (P.L. 114-328 2017). Accordingly, the
Department is moving from unique architectures and closed systems that are inflexible and cost-
prohibitive to architectures that include the use of open interface standards with modular systems
to facilitate continuous adaption and upgrades (Mattis 2018).
MOSA provides an integrated business and technical strategy for competitive and affordable
acquisition and sustainment of a new or legacy system (or a component within a new or legacy
system) over the system life cycle. The modular approach uses an architecture that separates the
system into major functions and elements, which work together across interfaces in conformance
with widely supported, consensus-based standards (Zimmerman et al. 2018).
1.1 Purpose of DoD MOSA Guidance
The Department intends its MOSA guidance to facilitate the adoption, integration, and refresh of
defense capabilities through the use of consensus-based standards, appropriate business practices,
and articulation of necessary data rights (P.L. 114-328 2017). MOSA should be at the foundation
of an acquisition program’s design strategy and architecture to address modernization, threat
response, mission integration, competition, resource savings, and security.
When implementing MOSA, programs must balance technical methods and business drivers.
Technical enablers such as standard interfaces allow architecture elements to evolve separately
and to interface with minimal impact to other system elements. MOSA couples the technical
design with open business practices such as selection and access to appropriate data, creating
opportunities to improve a system’s warfighting ability. In addition, programs need to balance
MOSA with safety and cybersecurity design characteristics, essential to maintaining a secure,
resilient system. The components can be incrementally added, removed, or replaced to provide
opportunities for cost savings or cost avoidance, resource reduction, technology refresh, capability
change, increased interoperability, increased competition, and easier sustainment of the system.
1.2 Preceding MOSA Efforts
The Department conducted earlier MOSA efforts through the Open Systems Joint Task Force
(OSJTF), which was established to provide focus and initial momentum to open system design and
use in DoD. At the time the Department defined open systems architecture as a characteristic of