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Modular Open Systems Approach (MOSA)

ALCL 088
Alternate Definition

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.
Alternate Definition Source

Title 10 USC 2446a.(b)Requirement for modular open system approach in major defense acquisition programs; definitions

Defense Standardization Program (DSP) MOSA webpage

General Information

The DoD’s MOSA is to design systems with highly cohesive, loosely coupled, and severable modules that can be competed separately and acquired from independent vendors. This approach allows the Department to acquire warfighting capabilities, including systems, subsystems, software components, and services, with more flexibility and competition. MOSA implies the use of modular open systems architecture, a structure in which system interfaces share common, widely accepted standards, with which conformance can be verified.

DoD is actively pursuing MOSA in the life-cycle activities of its MDAP, in large part due to the rapid evolution in technology and threats that require much faster cycle time for fielding and modifying warfighting capabilities. As part of a comprehensive systems engineering strategy, MOSA can accelerate and simplify the incremental delivery of new capabilities into systems.

Thus DoD MOSA is an integrated business and technical strategy to achieve competitive and affordable acquisition and sustainment of a new or legacy system or component over the system life cycle.


MOSA Benefits

This approach integrates technical requirements with contracting mechanisms and legal considerations to support a more rapid evolution of capabilities and technologies throughout the product life cycle through the use of architecture modularity, open systems standards, and appropriate business practices. DoD seeks five primary benefits of MOSA:

  1. Significant cost saving or avoidance
  2. Schedule reduction and rapidly deploy new technology
  3. Opportunities for technical upgrades and technical refreshment (tech refresh)
  4. Interoperability, including system of systems interoperability and mission integration
  5. Other benefits during the sustainment phase of a major system


Program Planning

Program Managers (PM) are expected to plan for implementing MOSA and to include a summary of such planning as part of the Systems Engineering Plan (SEP) and the overall Acquisition Strategy. The summary of the MOSA planning should address the following three areas:

  1. How MOSA fits into a program's overall acquisition process and strategies for acquisition, technology development, and test and evaluation
  2. What steps a program will take to analyze, develop, and implement a system or a system-of-systems architecture based on MOSA principles
  3. How the program intends to monitor and assess its MOSA implementation progress and ensure system openness


MOSA Enabling Standards

MOSA enabling standards can best be described as widely accepted, supported and consensus based standards set by recognized standards organizations or the marketplace. These standards support interoperability, portability, and scalability and are equally available to the public under fair and reasonable license terms. The Office of the Secretary of Defense (OSD) has determined continued implementation and further development of MOSA enabling standards are essential to the ability to rapidly share information across domains, with quick and affordable updates or improvements to both hardware and software components.

To prepare DoD for a MOSA future, OSD established the Modular Open Systems Working Group (MOSWG) and three MOSA Tiger Teams (Standards, Implementation Guidance, and Requirements & Programming Functions) to develop maturity assessments, deliver MOSA specific standards, conduct gap analysis, identify standard profiles, and deliver a MOSA Standards Needs Assessment. The three MOSA Tiger Teams were successful in meeting their objectives and have now been succeeded by a single standards tiger team that meets monthly. OSD will continue to work with standardization stakeholders, including DSP Office (DSPO) and the Departmental Standards Offices (DepSO), at these meetings to further identify MOSA enabling standards as they are developed.