Design Interface reflects the driving relationship between system design parameters to product support resource requirements.  Design interface analysis is based on digital system models and related digital product data that form the system's Authoritative Source of Truth. These design parameters are expressed in operational terms rather than as inherent values and specifically relate to system requirements. Thus, product support requirements are derived to ensure the system meets its availability goals and design costs and support costs of the system are effectively balanced.

Design Interface is the "integration" in the IPS Elements. When one askes the question "How does this requirement effect any of the IPS Elements?", one is practicing Design Interface. For example, suppose program engineers designed a part in a high-wear area out of plastic in order to save on cost and weight. This design effort may well impact several of the IPS Elements. Because the part is plastic and in an abusive area, it may require additional parts and maintenance, and thus may directly impact Supply Support, Manpower and Personnel, Support Equipment, and Packaging, Handling, Storage and Transportation (PHS&T).  It could also indirectly impact Facilities and Infrastructure (storage for the spares), Training and Training Support and has the potent to affect other elements as well. This can be described as the Design Interface 'arrow' emanating from design to the IPS Elements - but the arrow may actually be going two ways, and impact the engineering space as well. Given that sustainment is the most expensive part of life cycle costs (estimated at betwee 60 - 80% of total system costs), the life cycle logistician might argue that instead of making the part out of plastic, the program should design it out of a more durable material such as aluminum. That critical interplay or "integration" is Design Interface.

In terms of importance, Design Interface is only eclipsed by Product Support Management in rankings of the IPS Elements. Product Support Management is a game-changer in that it encompasses all functional areas of the program office  (life-cycle logistics, systems engineering, test and evaluation, etc.), while Design Interface is the connection between Product Support Managament and all those other functions.

Key Design Interface IPS Element activities according to Appendix A of the  Product Support Manager (PSM) Guidebook include:

• Standardization and interoperability
• Engineering data analysis
• Net-centric capability management
• Reliability, availability, maintainability (RAM) design
• Producibility
• Supportability/Sustainability
• Deployability management
• Human Systems Integration (HSI)
• Environmental management
• Warfighter/machine/software/interface/usability management
• Survivability and vulnerability management
• Affordability
• Modularity and Open Systems Approach (MOSA)
• Corrosion control and prevention
• Non-destructive inspection
• Hazardous material management
• Energy management
• Reliability Centered Maintenance (RCM)
• Risk Management

The activities of Design Interface begin during requirements definition of the system and continue throughout the system's life cycle. In each stage of the acquisition process, life cycle logisticians should  work with design and systems engineering, cost analysis, Test and Evaluation (T&E), Quality Control (QC) and all other pertinent program areas to ensure the system is focused on meeting the required product support objectives.

Design Interface is therefore a "leading activity" that may impact all other the IPS Elements.  A well-performed Design Interface effort is one that contributes to minimizing the logistics footprint and maximizing reliability, ensuring that maintenace is as user-friendly and effective as possible, for example. It also should address long-term issues related to Diminishing Manufacturing and Materiel Shortages (DMSMS), obsolescence management, technology refreshment, modifications and upgrades, and overall usage under all operating conditions.

The success of Design Interface is dependent upon program leadership and their recognition and resourcing of supportability efforts.  In addition, leaders need to communicate that long-term supportability is everybody's business - not just those in logistics positions. This is because supportability features cannot be easily "added-on" after the design is established and supportability should be accorded a high priority early in the program's planning and be integral to the system design and development process.