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Flow-Service-Quality (FSQ) Engineering: Foundations for Network System Analysis and Development

June 2002 Technical Note
Richard C. Linger (Oak Ridge National Laboratory), Mark Pleszkoch, Gwendolyn H. Walton, Alan R. Hevner (University of South Florida)

In this 2002 report, the authors describe Flow-Service-Quality engineering, an emerging technology for management, acquisition, and more.


Software Engineering Institute

CMU/SEI Report Number


DOI (Digital Object Identifier):


Modern society could hardly function without the large-scale, network-centric information systems that pervade government, defense, and industry. As a result, serious failures or compromises carry far-reaching consequences. These systems are characterized by changing and often unknown boundaries and components, constantly varying function and usage, and complexities of pervasive asynchronous operations. Their complexity challenges human intellectual control, and their survivability has become an urgent priority. Engineering methods based on solid foundations and the realities of network systems are required to manage complexity and ensure survivability. 

Flow-Service-Quality (FSQ) engineering is an emerging technology for management, acquisition, analysis, development, evolution, and operation of large-scale, network-centric systems. FSQ engineering is based on Flow Structures, Computational Quality Attributes, and Flow Management Architectures. These technologies can help provide stable engineering foundations for the dynamic and often unpredictable world of large-scale, network-centric systems. Flow Structures define enterprise mission task flows and their refinements into uses of system services in network traversals. Flows are deterministic for human understanding, despite the underlying asynchronism of network operations. They can be refined, abstracted, and verified with precision, and deal explicitly with Uncertainty Factors, including uncertain commercial off-the-shelf functionality and system failures and compromises. Computational Quality Attributes go beyond static, a priori estimates to treat quality attributes such as reliability and survivability as dynamic functions to be computed in system operation. Computational Quality Attribute requirements are associated with flows and can be dynamically reconciled with network service attributes in execution. Flow Management Architectures include design and implementation frameworks for dynamically managing flows and attribute requirements, as well as processes for their development. FSQ foundations are defined by theorems that illuminate engineering practices and automation opportunities.