Software Engineering Institute | Carnegie Mellon University
Software Engineering Institute | Carnegie Mellon University

CLIP Program Employs Quality Attribute Workshops and the Architectural Tradeoff Analysis Method

Tactical Data Links (TDLs) are used throughout the military services to provide real-time battlefield situational data about enemy positions and movements between various sensors, weapons platforms, aircraft, and other vehicles, providing continuously updated tactical displays for battlefield commanders and combatants.

The Common Link Integration Processing (CLIP) Program is a joint Air Force and Navy program that is leading the acquisition of a software package that allows existing platforms without a TDL, as well as platforms with different TDLs, to communicate with each other. When CLIP is installed, these platforms can exchange information digitally without having to rely on voice radio transmissions. Through the use of CLIP, platforms’ TDL life-cycle costs are reduced because common software components are used on all platforms.

"Had we not incorporated plans for addressing software architectural issues up-front, we would have been at risk of having to make major changes downstream in the program, which would substantially raise the costs for both us and the participating programs."

CLIP enables the transition of platforms to the Network Centric Warfare (NCW) environment by providing tactical networking and gateway functionality.


The CLIP program faces five main challenges: (1) developing software assets that can be ported to different platforms that use diverse hardware and software, (2) accommodating different techniques to forward data "intelligently" from multiple TDLs and/or Internet Protocol (IP); (3) providing interoperability between different versions of CLIP that are operationally fielded, (4) supporting different platform software integration need dates via the CLIP incremental acquisition, and (5) supporting the addition of new TDL formats without having to re-design the software. To address these challenges, the CLIP software must possess the following quality attributes (non-functional requirements):

  • Portability – CLIP is designed to be run on multiple types of computer processors with different operating systems and different timing constraints.
  • Modifiability/Scalability – CLIP platforms can be customized to use only the CLIP features that they require for their missions. These features include the ability to communicate via IP as well as with TDLs and selecting the type of data forwarding to implement.
  • Interoperability – Platforms running different versions of CLIP can communicate successfully.
  • Extensibility – CLIP is designed to support the addition of new TDL formats.

Approach and Results

To address these challenges, the CLIP program adopted an architecture-centric software acquisition approach. The SEI is supporting CLIP in this approach by conducting two Quality Attribute Workshops (QAWs) and a series of software architecture evaluations using the Architectural Trade-Off Analysis Method (ATAM). A QAW is a facilitated method for discovering the driving quality attributes of a system, such as availability, performance, security, interoperability, and modifiability. The QAW is being used proactively to identify the specific quality attributes CLIP requires before there is a commitment to a specific software architecture. ATAM is a complementary and proven architecture analysis method that is useful for identifying risks, sensitivities, and tradeoffs associated with how well an architecture is able to achieve specific quality attributes. By applying these methods to reduce software acquisition risk, the CLIP program will be one of the leading adopters of architecture analysis and evaluation in the DoD.

The first QAW for CLIP was conducted with government-only stakeholders. It was completed in 2003, prior to releasing the request for proposal (RFP) and resulted in the generation of a prioritized set of quality attribute scenarios that represent the system qualities that are critical to the success of CLIP. These results were further used to refine the CLIP system requirements and steer the RFP technical evaluation criteria. A second QAW was conducted with both government and contractor stakeholders following contract award to develop a set of prioritized quality attribute scenarios that are being used to guide the software architecture development in support of the system’s desired qualities.

A series of ATAM-based software architecture evaluations are scheduled for the contract performance phase as a software risk reduction measure. The SEI will assist in this effort by conducting the initial evaluation during the development of the first software increment and providing support to the evaluations during each subsequent software increment. Eventually, the evaluations will become the responsibility of the development contractor, to be performed under the oversight of the program office. The SEI has also supported process improvement in the CLIP program by providing Capability Maturity Model Integrated (CMMI) training and leading the initial Standard CMMI Assessment Method for Process Improvement (SCAMPI) Class B appraisal.

The SEI began supporting the CLIP program early in the RFP preparation stage, which is where many of the issues that can subsequently plague software acquisition efforts need to be mitigated. The SEI’s support of CLIP includes ongoing participation in the CLIP Integrated Product Team to assist in the oversight of the CLIP acquisition

Thomas Ryan, the CLIP assistant program manager, has been pleased with the close support the SEI has provided and with the quality and relevance of the technologies being applied to the program. "Had we not incorporated plans for addressing software architectural issues up-front, we would have been at risk of having to make major changes downstream in the program, which would substantially raise the costs for both us and the participating programs," he commented, adding that "SEI is the best kept secret in DoD!"