"Page:1 System Requirements Definition System Requirements Definition Process Department of Engineering Management & SystemsEngineering (EMSE) Dr. Gina Guillaume-JosephPage:2 System Requirements Definition These slides were developed to present and amplify the content ofINCOSE’s Handbooks and as such incorporate text and graphics from thehandbooks.These items retain INCOSE’s copyrights statement: © 2015 INCOSE. All RightsReserved. May not be copied,scanned, or duplicated, in wholeor in part, except for use aspermitted in a license obtainedfrom INCOSE for classroom use.Page:3 System Requirements Definition Agenda ? Context ? Purpose ? Key Activities ? OutcomesPage:4 System Requirements Definition Context Not consideringBusiness orDisposal the business /UnexpectedMission Analysis environment emergence Stakeholder NeedsOperation Maintenance & Reqts Definition Insufficient System ReqtsValidation Analysis Definition Poorcommunication Not enough Architecture UnexpectedTransition Definition alternatives emergence DesignGetting here Verification Definition too quickly – orstarting here UnexpectedIntegration System Analysis emergence SE Process Producibility Implementation Challenges issuesPage:5 System Requirements Definition Requirements: The Big Picture ISO 15288:2015 Processes Business or Mission Analysis Concept of Need Operations Stakeholder Needs & Reqts Definition Derived Allocated ArchitectureRequirements Architecture System ReqtsDefinition Mission Definition Requirements System System DesignStakeholders’ Requirements Definition Requirements Component Components Requirements Configuration Item Configuration Items Requirements Integration and Qualification Systems Adapted from The Engineering Design of Systems, Buede, 2009Page:6 System Requirements Definition Transforming Needs into Requirements Source: SEH v4 p. 48Page:7 System Requirements Definition System Requirements Definition Process ? Purpose – Transform the stakeholder, user-oriented view ofdesired capabilities into a technical view of a solution that meetsthe operational needs of the user • System requirements are the foundation of the systemdefinition • They form the basis for the architecture definition, designdefinition, integration, and verification processes • Each requirement comes with a cost – even to manage • Shoot for a complete but minimum set established fromstakeholder requirements • These reflect the supplier’s perspective • Specify the system characteristics, attributes, functions, andperformance needed to meet the stakeholder requirements • Iterative and recursive process • Avoiding implementation biases Source: SEH v4 p. 58Page:8 System Requirements Definition The Emerging Voice of the Solution Requirement (What) Design (How) ? Need to observe 1000 square ? Some sort of UAV looks best kilometers of denied territoryStakeholder need per day ? The UAV shall provide the? Mission is day/night and willcapability to observe 1000 squse a multirole sensor km / day under all lightingconditions Allocated requirements ? A scanning EO sensor with? The UAV mounted multirolelow-light capacity will worksensor shall support a framehere rate of X frames / hour Lifecycle DepthPage:9 System Requirements Definition Iterative and Recursive Definition ? A complex process employing performance analysis, tradestudies, constraint evaluation and cost/benefit analysis ? System requirements cannot be established withoutdetermining their impact (achievability) on lower level elements ? Requirements definition and analysis is an iteration andbalancing process that works both “top-down” (called allocationand flowdown) and “bottom-up”? Once the top-level set of system requirements has beenestablished, it is necessary to allocate and flow them down tosuccessively lower levels Source: SEH v4 p. 60Page:10 System Requirements Definition System Requirements Definition Process Source: SEH v4 p. 58Page:11 System Requirements Definition Key Activities 1. Prepare for system requirements definition 2. Define system requirements 3. Analyze system requirements 4. Manage the system requirements definition process Source: SEH v4 p. 58Page:12 System Requirements Definition 1 Prepare for System Requirements Definition ? Establish the approach for defining systemrequirements ? Methods, tools, expertise, documentation needs ? Quality criteria, templates, formats ? In conjunction with the Architecture Definitionprocess, determine the system boundary ? Includes interfaces and expected interaction of the system withexternal systems ? Reflecting operational scenarios and expected system behaviors Source: SEH v4 p. 59Page:13 System Requirements Definition Define Systems Capabilities 1 and Performance Objectives ? Very important to derive and identify system constraints andperformance objectives as this will drive the requirementsanalysis approach ? Think towards system production, deployment, operations ? Typical constraints on the system: - Cost and schedule - Mandated use of commercial off-the-shelf (COTS) technology - Operational environment and use of pre-existing facilities and systemelements - Operational interfaces with other systems or organizations Source: SEH v3.2.2 p. 82Page:14 System Requirements Definition Define Systems Capabilities 1 and Performance Objectives ? Analysis is likely to explore areas such as power, propulsion, communications, data processing, environmental and human interaction, and intervention ? Assisted greatly by: - Modeling and Simulation - Interdisciplinary requirements audit Source: SEH v3.2.2 p. 82 Rolls RoycePage:15 System Requirements Definition Key Activities Cont’d 1. Prepare for system requirements definition 2. Define system requirements 3. Analyze system requirements 4. Manage the system requirements definition process Source: SEH v4 p. 58Page:16 System Requirements Definition 2 Define System Requirements - BLUF ? Identify stakeholder requirements or organizational limitations thatimpose unavoidable constraints, capture these ? Identify and define the required system functions ? Also include lifecycle functions and system behavioral characteristics ? Identify critical quality characteristics such as safety, security, reliability,and supportability ? Identify technical risks ? Specify system requirements consistent with stakeholder requirementsand derived functional boundaries, functions, constraints, criticalperformance measures, critical quality characteristics, and risks ? Capture rationale with each requirement ? Place all this in the SyRS and supplement with a document tree if needed Source: SEH v4 p. 59Page:17 System Requirements Definition Define / Derive / Refine 2 Functional / Performance Requirements ? So far the focus has been on translating user needs into: - Basic functions - A quantifiable set of performance requirements … that can be translated into design requirements ? This next process will define, derive, and/or refine the total system requirementsover the system’s life cycle, including its support requirements ? Requirements will now be formally documented defining functions andinterfaces and will characterize the system by performance requirements thatcan be flowed down to hardware and software designers Source: SEH v4 p. 63Page:18 System Requirements Definition 2 Define /Derive / Refine Functional /PerformanceRequirements The primary focus through SystemRequirements Review [SRR] Involves the component disciplines Involves the customer! Requirements Derivation, Allocation, and Flowdown Source: SEH v3.2.2 p. 84Page:19 System Requirements Definition Define / Derive / Refine 2 Functional / Performance Requirements 1. Start with the source requirements, establish constraints onthe system from:- Cost - Schedule - Use of Commercial Off-The-Shelf (COTS) equipment - Use of Non-Development Items (NDI) - Use of Existing Facilities - Operational Interfaces with other systems or organizations - Operational environment Performance and Functional Requirements Source: SEH v3.2.2 p. 84Page:20 System Requirements Definition Define / Derive / Refine 2 Functional / Performance Requirements 2. Examine the Mission, characterize it quantitatively: - Quality, quantity, coverage, timeliness, and availability ? Expand the analysis out to consider the total system inits deployment environment: - Communications - Supportability Performance, - Logistics Functional, - Command and control InterfaceRequirements - Security Source: SEH v3.2.2p. 85"