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Systems Engineering and Architecture

Systems Engineering and Architecture

Modular Open Systems Approach

MOSA stakeholders graphic.
The MOSA ecosystem depends on active involvement by multiple stakeholders across the Department of Defense.

A Modular Open Systems Approach (MOSA) is an integrated business and technical strategy to achieve competitive and affordable acquisition and sustainment over the system life cycle. In the development of Department of Defense (DoD) systems, MOSA is an acquisition and design strategy, consisting of technical architectures, that adopts open standards and supports a modular, loosely coupled, and highly cohesive system structure.

MOSA implies the use of a modular design, including system interfaces designed according to accepted standards with which conformance can be verified. MOSA can be employed in both defense and non-defense sectors by using a modular architecture and an open business model to add, modify, replace, and remove system components across the acquisition life cycle.

DoD can use MOSA to design systems with highly cohesive, loosely coupled, and severable modules that can be competed separately and acquired from independent vendors. DoD is actively pursuing MOSA in the life cycle activities of its Major Defense Acquisition Programs and Major Automated Information Systems, keeping pace with the rapid evolution in technology and threats that require faster cycle time for fielding and modifying warfighting capabilities.

A key enabler for MOSA is the adoption of an open business model, which requires doing business in a transparent manner and leveraging the collaborative innovation of numerous participants across the DoD enterprise. The open business model permits sharing risk, maximizing reuse of assets, and reducing ownership cost. MOSA allows the Department to incrementally acquire warfighting capabilities, including systems, subsystems, software components, and services, with more flexibility, competition, and innovation.

Working Groups

To further the use of MOSA in defense programs, DoD Engineering leads a collaborative Modular Open Systems Working Group (MOSWG), whose participants represent multiple segments of the defense engineering and acquisition community, including Program Executive Offices, Program Managers, engineering, and science and technology proponents. The MOSWG promotes modular open engineering principles through the Services and other agencies and can assist in advancing modular open practices.

As a resource for MOSA practitioners in Government, industry, and academia, DoD Engineering manages the Modular Open Systems Community of Practice (CoP) website, hosted by Defense Acquisition University (DAU). The CoP site is open to the public. Users with a DoD Common Access Card may register with DAU and contribute comments and other content to the site.

MOSA Touch Points graphic
MOSA is involved in many areas in engineering across the system life cycle.

Modular Open Systems Working Group (MOSWG)

Membership: Program Executive Officers, Program Managers, engineers, science and technology components


Training and Education Resources

CLE 019 (DAU): This course describes MOSA principles from a business and technical perspective. It provides program examples of successful MOSA implementation, as well as sources that can assist an organization in implementing MOSA. This course is designed to familiarize students with MOSA best practices throughout the life cycle.


The Tri-Service Tiger Team reviewed and updated the following definitions, which can be found in the DAU Glossary.

Contact Us

For more information, contact  using the following subject line: Attn SE&A /MOSA

Office of the Under Secretary of Defense,
Research and Engineering (OUSD(R&E))
3030 Defense Pentagon, Washington, DC 20301-3030