What is MOSA?

A Modular Open Systems Approach (MOSA) is a modular design approach that utilizes open standards for the development of an affordable and adaptable system. The Department of Defense (DoD) adopted MOSA to design systems with highly cohesive, loosely coupled, and severable modules that can be competed separately and acquired from independent vendors. 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. This approach allows the DoD to acquire warfighting capabilities, including systems, subsystems, software components, and services, with more flexibility from multiple vendors.

Modular Open Systems Approach (MOSA) Standards

As the key to the design of open systems is the use of open standards, the DoD Information Technology Standards Registry (DITSR) mandates the minimum set of standards and guidelines for the acquisition of all DoD systems that produce, use, or exchange information. The standards used for MOSA are 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.

Principles of Modular Open Systems Approach (MOSA)

Programs for the development of Defense systems design their system based on adherence to the following MOSA principles:

• Establishing an enabling environment with supportive requirements, business practices, technology development, acquisition, test & evaluation, and product support strategies needed for the effective development of open systems.
• Employing modular designs that are:
  • Cohesive - containing well-focused and well-defined functionality
  • Encapsulated - hide the internal workings of a module’s behavior and its data
  • Self-contained - do not constrain other modules
  • Highly binned - use broad modular definitions to enable commonality and reuse
• Designate key interfaces that should be grouped into key and non-key interfaces. This enables designers and configuration managers to distinguish among interfaces that exist between technologically stable and volatile modules, between highly reliable and more frequently failing modules, between modules that are essential for net-centricity and those that do not perform net-centric functions, and between modules that pass vital interoperability information and those with least interoperability impact.
• Using open interface standards that are well defined, mature, widely used, and readily available.
• Certifying conformance by rigorous and well-established assessment mechanisms, well-defined interface control and management, and proactive conformance testing to verify, validate and ensure the openness of systems. Validation and verification mechanisms such as conformance certification and test plans ensure that the system and its component modules conform to the external and internal open interface standards allowing plug-and-play of modules, net-centric information exchange, and re-configuration of mission capability in response to new threats and evolving technologies.

Open systems characteristics and principles address:

• Design requirements like mandated open standards and protocols
• Derived requirements fulfilling the need for open interfaces to enable interoperability
• Design constraints, for example, the complexity of adhering to open interface specifications as system components are designed
• Architectural attributes that are adaptable, upgradeable, and reconfigurable system architecture
• Designs that take into consideration modular and open systems design benefits and concerns
• Business strategies to gain access to competitive sources of supply and effectively manage technological obsolescence.

Benefits of Modular Open System Approach (MOSA):

There is no single primary benefit for the implementation of MOSA. Systems designed using MOSA have predetermined desired outcomes that fully realize its benefits which vary according to the implementation. The five primary benefits of MOSA:

• Enhance competition by using an open architecture with severable modules, allowing components to openly compete.
• Facilitate technology refresh that can be achieved with the delivery of new capabilities or replacement technology without changing all components in the entire system.
• Incorporate innovation by adding operational flexibility to configure and reconfigure available assets to meet rapidly changing operational requirements.
• Enable cost savings/cost avoidance by reusing technology, modules, and/or components from suppliers across the acquisition life cycle.
• Improve interoperability by, for example, allowing severable software and hardware modules to be changed independently.

Click here to read about SOSA or Sensor Open Systems Architecture.