A MOSA, formerly known as Open Systems Architecture or Open Systems Approach, can be defined as a technical and
business strategy for designing an affordable and adaptable system. A MOSA is the DoD preferred method for
implementation of open systems, and it is required by US law. Title 10 USC 2446a.(b), states all Major Defense
Acquisition Programs (MDAP) are to be designed and developed using a MOSA that:
- Employs a modular design that uses major system interfaces between a major system platform and a major system
component, between major system components, or between major system platforms;
- Is subjected to verification to ensure major system interfaces comply with, if available and suitable, widely
supported and consensus-based standards; and
- Uses a system architecture that allows severable major system components at the appropriate level to be
incrementally added, removed, or replaced throughout the life cycle of a major system platform to afford
opportunities for enhanced competition and innovation.