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Modular open systems approach: what is MOSA and how does it relate to AI for the defense sector?
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Art deco-inspired image uses hexagonal modules in dark blue and gold tones to symbolize the interconnected and modular nature of defense systems architecture. The symmetrical alignment and minimalistic highlights suggest the organized, adaptable, and high-tech qualities of a modular open system architecture (MOSA) for defense applications.

Modular open systems approach: what is MOSA and how does it relate to AI for the defense sector?

By Jacob Andra / Published October 28, 2024 
Last Updated: October 28, 2024

Executive summary:

Defense contractors face mounting pressure to deliver adaptable systems at the speed of technological change. China develops and fields capabilities five to six times faster than the U.S., according to a recent DoD assessment. To maintain technological superiority, the Department of Defense has mandated a modular open systems approach (MOSA) for major defense acquisitions.

Talbot West champions a MOSA-compliant paradigm to AI implementation. We call it “cognitive hive AI,” or CHAI. It’s an explainable, configurable, adaptable paradigm for deploying AI systems. If you’re interested in a MOSA approach to AI deployment, let’s talk.

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Main takeaways
China fields military tech five times faster than the U.S.
Proprietary systems face obsolescence before deployment.
Open interfaces speed updates and reduce costs.
MOSA needs culture change, not just standards.
Success requires strict governance of interfaces.

What is MOSA?

MOSA is an integrated business and technical strategy that breaks down monolithic systems into modules connected by open interfaces. Traditional defense systems often function as tightly integrated units that resist modification or upgrading. These systems take years to develop and often face obsolescence before achieving full operational capability.

MOSA addresses this problem through modularity and standardization. Like a modern smartphone that can download new apps or upgrade components independently, MOSA-compliant systems can integrate new capabilities without system-wide redesign.

The 2017 National Defense Authorization Act mandated MOSA for major defense acquisitions because:

  • Traditional acquisition cycles can't keep pace with rapidly evolving threats
  • Vendor lock-in through proprietary interfaces drives up costs and stifles innovation
  • Complex interdependencies make systems difficult to upgrade or maintain
  • Limited competition reduces incentives for innovation and cost control

The five pillars of MOSA

MOSA is based on the following five pillars:

  1. Establish enabling environment
  2. Employ modular design
  3. Design key interfaces
  4. Select open standards
  5. Certify conformance

Let’s look at each of these in more detail.

1. Establish enabling environment

Creating an enabling environment means fundamentally reshaping how organizations approach system development and acquisition. This goes far beyond technical specifications to encompass the entire organizational ecosystem.

The environment must integrate development and operations while enabling phased technology insertion and secure data sharing. Organizations need to transform their requirements, business practices, and management approaches to align with MOSA principles. This includes developing clear contracting language that mandates MOSA compliance and crafting data rights strategies that protect both government and industry interests.

Success requires strategic use of incentives, such as tying fees to verified MOSA compliance or linking sustainment support to delivery of technical data rights. Organizations must also invest in training programs and infrastructure that support modular development practices.

2. Employ modular design

Modular design creates highly cohesive, loosely coupled, and self-contained components. Each module should contain everything necessary for its function while limiting itself to only related components. This approach emphasizes clear boundaries and minimal external dependencies.

The core principle of modularity is that each module represents a single relevant concept and hides its implementation details behind well-defined interfaces. This encapsulation enables parallel development efforts and accommodates future uncertainty. Modules can be separately procured from independent vendors, tested and validated independently, and updated or replaced without disrupting the broader system.

This approach contrasts sharply with traditional systems where components are tightly interwoven. MOSA's modular design philosophy enables innovation by allowing different vendors to compete at the module level, while ensuring that individual improvements can be integrated without system-wide redesign.

3. Designate key interfaces

Key interfaces serve as the critical boundaries between major system components, whether between platforms, between components, or between platforms and their components. These interfaces require precise definition and thorough documentation to enable true interoperability.

Each interface must specify not just its technical parameters but its semantic meaning - what the interface does and how it behaves. This documentation includes machine-readable definitions and clear descriptions of how the interface relates to existing standards. Version control and compatibility management ensure that systems can evolve while maintaining functional connections.

The success of MOSA depends heavily on these interfaces being stable, accessible, and verifiable. When properly implemented, they allow programs to maintain current functionality while incrementally improving capabilities through module updates and replacements.

4. Select open standards

MOSA relies on standards that have broad industry support and validation from recognized organizations. The Defense Standardization Program has established MOSS (Modular Open Standards and Specifications) as a dedicated repository for MOSA-enabling standards, including everything from interface specifications to implementation practices.

These standards must be mature, proven in use, and regularly maintained. They should enable interoperability across vendors while facilitating technology insertion and system evolution. The focus on open standards reduces dependency on proprietary solutions while promoting competition and innovation.

Standard selection requires careful evaluation of industry support, technical maturity, and long-term viability. Programs must balance the benefits of newer standards against the stability of established ones, always keeping in mind the goal of reducing lifecycle costs while maintaining system effectiveness.

5. Certify conformance

Conformance certification moves beyond basic interoperability testing to verify that modules fully implement standard interfaces and behaviors as specified. This process requires clear criteria, robust verification procedures, and regular revalidation as systems evolve.

Programs must develop specific measures of effectiveness and performance that reflect their operational requirements while ensuring compliance with MOSA principles. Testing should verify not just interface implementation but also functional behavior, performance requirements, and security controls.

The goal of certification isn't just to ensure quality - it's to enable competition while maintaining reliability. Regular revalidation ensures that systems maintain compliance as they evolve, protecting the benefits of the MOSA approach throughout the system lifecycle.

The strategic and practical benefits of MOSA

The image illustrates interconnected nodes, each containing detailed control panels, symbolizing different modular components within a system architecture. The circular nodes, linked by bright lines, represent the communication pathways in a modular open system architecture (MOSA), emphasizing interoperability and data flow between systems. The networked design visually reinforces the collaborative and integrated nature of MOSA, showcasing how diverse modules interact seamlessly within a unified framework.

MOSA fundamentally transforms how defense systems are acquired, maintained, and upgraded. As implementations mature across programs, the benefits compound through a growing ecosystem of compatible modules and experienced vendors.

Breaking vendor lock

Traditional defense acquisitions often result in vendor lock, where single contractors control proprietary interfaces. This monopoly position leads to inflated prices and slow innovation cycles. MOSA breaks this cycle by enabling competition at the module level. The U.S. Navy's Submarine Warfare Federated Tactical System demonstrates this benefit - its open architecture allowed multiple vendors to bid on system components, driving down costs while accelerating innovation.

Faster capability deployment

The U.S. Army's Modular Active Protection System (MAPS) showcases MOSA's impact on deployment speed. Using a government-owned base kit, MAPS rapidly integrates new sensors and countermeasures as threats emerge. Rather than waiting years for complete system upgrades, defense organizations can deploy improvements as individual modules become ready. This agility proves crucial in an era of rapidly evolving threats.

Streamlined maintenance

When components are clearly separated with standardized interfaces, maintenance becomes more efficient and cost-effective. The Hardware Open Systems Technology (HOST) initiative demonstrates this advantage - HOST-compliant systems enable quick module replacement without affecting other components. This modularity reduces downtime and simplifies logistics through standardized replacement parts.

Enhanced interoperability

MOSA's standardized interfaces naturally promote cross-system compatibility. The Future Airborne Capability Environment (FACE) consortium shows how this works - FACE-compliant software components can be reused across different aircraft platforms, reducing development costs while ensuring systems work together effectively.

Technology reuse and adaptation

Modules developed for one program can be rapidly adapted for others, spreading development costs across multiple applications. This reuse accelerates innovation while reducing costs. The Defense Standardization Program's Modular Open Standards and Specifications (MOSS) repository accelerates this sharing by providing a central source for MOSA-enabling standards.

Growing vendor expertise

As vendors gain experience with MOSA standards and practices, integration expertise builds across the industrial base. This expanding knowledge pool makes each new implementation more efficient than the last. Competition intensifies as more vendors develop MOSA capabilities, driving continued innovation and cost reduction.

Reduced barriers to entry

Standardized interfaces and well-documented requirements make it easier for new vendors to enter the market. This increased competition spurs innovation while giving defense programs more options for capability development and sustainment.

Long-term strategic value

MOSA's benefits compound over time through network effects. Each successful implementation expands the ecosystem of compatible modules, experienced vendors, and proven standards. Programs implementing MOSA today both benefit from and contribute to this growing ecosystem.

The creation of the MOSS standardization area further accelerates these benefits by encouraging convergence on common approaches. This standardization helps programs identify and implement appropriate standards while reducing fragmentation in the industrial base.

Organizations that embrace MOSA position themselves to leverage a broadening ecosystem of innovation while maintaining control of their technical baseline. The documented successes across multiple programs and domains demonstrate that MOSA delivers measurable, sustained benefits in cost, speed, and capability.

Modular Open Systems Approach in action

The success of MOSA has been extensively documented across multiple defense programs. Let's examine some key implementations that demonstrate its concrete benefits.

VICTORY initiative success

The Vehicle Integration for C4ISR/EW Interoperability (VICTORY) initiative shows how MOSA principles transform ground vehicle electronics integration. Before VICTORY, each new electronic system required its own display, processors, and power systems. This "bolt-on" approach led to increased size, weight, and power consumption while limiting interoperability.

VICTORY's standardized data bus architecture enables vehicles to share hardware resources like displays and processors. This sharing has achieved documented reductions in integration costs and timeline compression for new capabilities. When the Army needed to add new electronic warfare capabilities to existing vehicles, VICTORY-compliant systems integrated in weeks rather than months.

MAPS: rapid threat response

The Modular Active Protection System (MAPS) framework demonstrates MOSA's value for rapid capability insertion. MAPS uses a government-owned base kit that can quickly incorporate different sensors and countermeasures. Key achievements include:

The MAPS framework has validated MOSA's ability to speed development cycles. Its reference implementation guide helps developers leverage the architecture for new active protection systems, while its compliance test suite ensures reliable integration of new modules. This standardization has led to documented acceleration in deploying new protective capabilities against emerging threats.

Navy's FACE implementation

The Future Airborne Capability Environment (FACE) initiative has revolutionized avionics software development. The Navy has documented significant cost savings through software reuse across different aircraft platforms. FACE-conformant components have demonstrated portability between different systems, reducing development time for new capabilities.

The FACE technical standard enables rapid integration of new avionics functions while maintaining backward compatibility. This approach has proven particularly valuable for upgrading legacy aircraft with modern capabilities without complete system overhauls.

C4ISR/EW CMOSS success

The C4ISR/EW Modular Open Suite of Standards (CMOSS) shows how MOSA enables hardware consolidation and rapid technology insertion.

By standardizing hardware interfaces and form factors, CMOSS allows rapid insertion of new capabilities while reducing the physical footprint of electronics systems. The initiative has documented reductions in size, weight, and power consumption while improving the speed of capability upgrades.

Air Force Open Mission Systems

The Air Force's Open Mission Systems (OMS) initiative demonstrates MOSA's impact on aircraft systems integration. OMS has enabled rapid integration of new sensors and mission systems across multiple aircraft types. The standardized interfaces have reduced integration timelines and costs while enabling competition among vendors for system upgrades.

CHAI: applying MOSA to AI

The image combines hexagonal modules with the figure of a bee, symbolizing a highly organized and interconnected system similar to a beehive. The dark blue and gold hexagonal shapes represent modular AI components within a MOSA (Modular Open System Architecture), emphasizing adaptability and efficient integration. The bee serves as a metaphor for collaborative intelligence, highlighting the coordinated and flexible nature of a MOSA-compliant AI system.

Cognitive hive AI (CHAI) extends MOSA principles to artificial intelligence implementation. Like MOSA, CHAI uses modular architecture and open standards to create flexible, explainable AI systems. This approach breaks AI capabilities into discrete modules that can be independently developed, tested, and deployed.

The modular nature of CHAI enables the following advantages:

  • Enhanced security through isolated components
  • Better explainability and governance
  • Faster deployment and updates
  • Lower computational requirements
  • Reduced vendor dependency

Read how CHAI benefits defense applications.

Why Talbot West for CHAI implementation

At Talbot West, we specialize in implementing CHAI solutions through our CHAI architecture. Our team brings deep expertise in both defense systems and artificial intelligence. We guide organizations through the entire process, from assessing needs and designing architectures to selecting standards and developing governance frameworks. Our approach ensures secure deployment with ongoing monitoring and optimization.

MOSA FAQ

Implementing MOSA sometimes requires higher upfront investment than traditional approaches. However, these costs are typically offset by reduced lifecycle costs through increased competition, simplified maintenance, and faster capability insertion. The key is taking a long-term view of system costs rather than focusing solely on initial development.

Well-designed modular systems can match or exceed the performance of traditional integrated systems. While poorly implemented modularity might introduce overhead, proper interface design and system architecture minimize these impacts. Programs like the Army's MAPS demonstrate that MOSA can deliver high performance while maintaining flexibility.

Modularity refers to breaking systems into independent, self-contained components. "Open" refers to using publicly available, consensus-based standards for interfaces between those modules. A system can be modular without being open (using proprietary interfaces), but MOSA requires both characteristics to enable true competition and innovation.

MOSA includes specific provisions for security. The architecture can incorporate security controls at module boundaries, and interface standards include security requirements. Programs can implement different security levels for different modules while maintaining overall system security. The key is designing security into the architecture from the start rather than adding it later.

The best time to implement MOSA is at program inception, when architectural decisions have the most impact. However, existing programs can adopt MOSA principles incrementally during major upgrades or technology refresh cycles. The key is developing a clear transition strategy that balances immediate needs with long-term MOSA benefits.

MOSA requires careful balance of government and industry intellectual property rights. While interface specifications must be open and available, vendors can maintain proprietary implementation details within modules. Programs need clear data rights strategies that protect both government interests and industry investment in innovation.

The choice of standards depends on your specific domain and requirements. The Defense Standardization Program's MOSS repository provides a starting point for identifying relevant standards. Programs should prioritize widely supported, mature standards that align with their technical and business objectives.

Programs need robust conformance testing and verification processes. This includes clear requirements in contracts, specific conformance criteria, and regular testing throughout development and deployment. Many successful MOSA implementations tie contract incentives to verified MOSA compliance.

Yes, MOSA has been successfully implemented in safety-critical systems including aircraft and combat vehicles. The key is incorporating safety requirements into interface standards and ensuring proper verification of safety-critical modules. The FACE consortium demonstrates how MOSA can work in safety-critical avionics.

Successful MOSA implementation requires a mix of technical and business expertise. Teams need understanding of:

  • Systems engineering and architecture
  • Interface design and standardization
  • Acquisition strategies and contracting
  • Test and verification methods
  • Program management

Many organizations work with experienced partners to build internal MOSA expertise over time.

Initial benefits such as increased competition can appear quickly, while others like reduced lifecycle costs accumulate over time. Programs typically see significant advantages within their first major upgrade or technology insertion cycle. The key is maintaining consistent MOSA implementation to realize long-term strategic benefits.

Resources

  • Defense Standardization Program. (n.d.). DSP :: MOSA. https://www.dsp.dla.mil/Programs/MOSA/
    Martin, V. (2024, July 9). Modular Open Systems Approach. https://www.cto.mil/sea/mosa/
  • Modular Open Systems Approach (MOSA). (n.d.). DAU. https://www.dau.edu/acquipedia-article/modular-open-systems-approach-mosa
  • Modular Open Systems Approach (MOSA). (n.d.-b). https://www.dau.edu/cop/mosa
  • Gold, R. & Office of the Deputy Assistant Secretary of Defense for Systems Engineering (ODASD(SE)). (2016). Improving Transition: Modular Open Systems Approach (MOSA) & Engineering Enablers. In 19th Annual NDIA Systems Engineering Conference [Conference-proceeding; PDF]. https://www.cto.mil/wp-content/uploads/2023/06/MOSA-Gold-2016.pdf
  • Zimmerman, P., Ofori, M., Barrett, D., Soler, J., & Harriman, A. (2018). Considerations and examples of a modular open systems approach in defense systems. The Journal of Defense Modeling and Simulation Applications Methodology Technology, 16(4), 373–388. https://doi.org/10.1177/1548512917751281
  • Spencer, R. S., Wilson, H. W., & Esper, M. E. (n.d.). Modular Open System Approach. In https://www.dsp.dla.mil/Portals/26/Documents/PolicyAndGuidance/Memo-Modular_Open_Systems_Approach.pdf.
  • Department of Defense Open Systems Architecture Data Rights Team. (2013). Employment of Open Systems Architecture Contract Guidebook for Program Managers, Version 1.1 [Contract Guidebook]. In Department of Defense Open Systems Architecture Data Rights Team. https://www.acqnotes.com/Attachments/Open%20System%20Architecture%20%28OSA%29%20Contract%20Guidebook%20for%20Program%20Managers%20June%2013.pdf
  • MODULAR OPEN SYSTEM APPROACH IN DEVELOPMENT OF MAJOR WEAPON SYSTEMS. (2019). In United States Code, Subtitle B—Department of Defense Acquisition Agility. https://ac.cto.mil/wp-content/uploads/2020/06/FY17_NDAA_Sec805_MOSA_PublicLaw_114-328-1.pdf
  • Deputy Director for Engineering, Office of the Under Secretary of Defense for Research and Engineering, Director of Defense Research and Engineering for Advanced Capabilities, Office of the Under Secretary of Defense Research and Engineering, Department of Defense, U.S. Air Force, U.S. Army, U.S. Navy, National Reconnaissance Office, Defense Acquisition University, & Joint Tactical Networking Center. (2020). Modular Open Systems Approach (MOSA) Reference Frameworks in Defense Acquisition Programs. https://www.cto.mil/wp-content/uploads/2023/06/MOSA-Framework-2020.pdf
  • Geier, N. & Office of the Under Secretary of Defense for Research and Engineering (OUSD(R&E)). (2022). OUSD(R&E) MOSA Assessment Criteria. https://www.cto.mil/wp-content/uploads/2023/06/MOSA-Assess-2022.pdf

About the author

Jacob Andra is the founder of Talbot West and a co-founder of The Institute for Cognitive Hive AI, a not-for-profit organization dedicated to promoting Cognitive Hive AI (CHAI) as a superior architecture to monolithic AI models. Jacob serves on the board of 47G, a Utah-based public-private aerospace and defense consortium. He spends his time pushing the limits of what AI can accomplish, especially in high-stakes use cases. Jacob also writes and publishes extensively on the intersection of AI, enterprise, economics, and policy, covering topics such as explainability, responsible AI, gray zone warfare, and more.
Jacob Andra

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