Flow-Service-Quality (FSQ) Requirements Engineering For High-Assurance Systems

Modern society could hardly function without the largescale, network-centric information systems that pervade government, defense, and industry. These systems exhibit shifting boundaries, often-unknown component behavior, constantly varying function and usage, and pervasive asynchronous operations. Their complexity challenges intellectual control, and their survivability has become an urgent priority. Requirements engineering methods based on solid theoretical 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 requirements specification, development, and evolution of network-centric systems. FSQ engineering is based on Flow Structures, Computational Quality Attributes, and Flow Management Architectures. These technologies can provide stable engineering foundations for the dynamic and unpredictable world of large-scale network systems. Flow Structure requirements define mission task flows and their refinements into uses of system services in network traversals. Flows are deterministic for human understanding, despite the asynchronism of network operations. They can be refined, abstracted, and verified with precision, and deal explicitly with uncertainty factors, including uncertain COTS functionality and system failures and compromises. Computational Quality Attributes go beyond static, a priori estimates to define requirements for quality attributes such as reliability and survivability as dynamic functions to be computed in system operation.