1. Refined ECSS Software Process Model for Critical SW Critical SW Case Study

2. Critical Software Critical Software Process Model Elements Project Phasing & Planning Critical Software System Requirements Engineering SW Criticality analysis Critical Software Requirements Engineering Process System Requirements Analysis of Critical Software

3. Critical Software - Tailored Project Phasing & Planning ProcessT Elements of SW Maintenance Plan Requirements Baseline at SRR Documentation Standards Design Standards Verification and Validation Standards Software Project Development Plan Parent: Critical Software Development Process Perspective: Software Engineering Activity: Project Phasing and Planning Diagram: 4 / CRT External References: ECSS-E-40, ECSS-Q-80 In Triggers (IT)Out Triggers (OT)External Inputs (EI) EI1: SW PA Plan Review EI2: SW PA Procedures & Standards Review EI3: SW PA Life Cycle Review External Outputs (EO) Requirements Baseline at SRR Software Project Development Plan (Life cycle, tools and methods definition) Software Life Cycle Definition (milestones, reviews and maintenance planning) SLC-1 E-40: 5.3.2.1 Documentation/Inputs- Output Process definition for each phase and Milestone SLC-3 E-40: 5.3.2.2 SRR SUPPLIER ECSS-M-30 PROJECT RQMTS ECSS-E_40 Sec 4.5 System vs Software Requirements Requirements Baseline SW Project Development Plan SUPPLIER Definition of Software Engineering Standards SLC-2 E-40: 5.3.2.11 Requirements Baseline SW Project Development Plan SUPPLIER Software Project Development Plan Review EI1 EI2 EI3 Analysis of applicability of critical SW standards to the project T Dependability & Safety specific Standards & Process Requirements (CUSTOMER) / SUPPLIER

4. Critical Software - Tailored Software System Requirements Engineering ProcessT Overall System Requirements RB (inputs to) IRD (inputs to) Electrical Design Spec PICA Spec Parent: Critical Software Development ProcessPerspective: Software Engineering Activity: Critical SW System Requirements Eng.ng Diagram: 12 / CRT External References: ECSS-E-40 sec. 5.2.2, 5.2.3, 5.2.4, 5.2.5 In Triggers (IT)Out Triggers (OT)External Inputs (EI)External Outputs (EO) System level Rqmts for SW Verification and Validation SE –3 E-40 sec. 5.2.4 SRR Critical SW System Requirements Analyis SE –1 E-40 sec. 5.2.2 System Partitioning SE-2 E-40 sec. 5.2.3 CUSTOMER System level Integration of Software SE –4 E-40 sec. 5.2.5 CUSTOMER SRR Data Package RB, IRD DJF RB: V&V Process requirements, including Test Requirements for Critical SW RB (inputs to) IRD (inputs to) Reviewed SRR Data Package RB, IRD DJF Software Criticality Analysis T Test Planning for Critical Software T Software Criticality Analysis Consolidation T SW Support Spec SW Criticality analysis Inputs to SW Project development plan

5. Critical Software - TailoredT Parent: Critical SW System Requirements Engineering Perspective: Software Engineering Activity:SW Criticality analysis Diagram: 12.1/ CRT External References: In Triggers (IT)Out Triggers (OT)External Inputs (EI)External Outputs (EO) SUPPLIERCUSTOMER Definition of SW Categorization Check Of Categorization applicability to projected SW System Spec (PICA Spec) Proposed categorization Supplier feedbacks SW Criticality analysis Inputs to SW Project development plan

6. Activity: Critical SW System Requirements Analysis Diagram: 13 / CRT Critical Software - Tailored System Requirements Analysis ProcessT RB: Functions & Performance Rqmts IRD: Interface Rqmts Parent: Critical SW System Requirement Engineering Process Perspective: Software Engineering External References: ECSS-E-40 sec. 5.2.2.1, 5.2.2.2, 5.2.6.2 In Triggers (IT) Out Triggers (OT) External Inputs (EI)External Outputs (EO) Definition of system functionalities and interfaces SYS-1 E-40 sec. 5.2.2.1 Overall system reqmts Operations and Maintenance Requirements Definition SYS-2 E-40 sec. 5.2.2.1, 5.2.6.2 V&V Rqmts and Design Constraints SYS-3 E-40 sec. 5.2.2.1 System Criticality / Critical Functions Definition SYS-4 E-40 sec. 5.2.2.2 RB:- Safety & Reliability Rqmts - Critical functions identification RB: Design Constraints V&V requirements - SW Eng. Standards RB: Operations and maintenance requirement RB (inputs to) IRD (inputs to) CUSTOMER Dependability & Safety Specific Requirements Definition for Critical Software T RB: Dependability/Safety Requirements for Critical SW Requirements CUSTOMER

7. Critical Software - Tailored Software Requirements Engineering ProcessT Activity: SW Requirements Engineering Process DIAG.#15 / CRT TCS SRD SUPPLIER External References: ECSS-E-40 sec.5.4.2, 5.4.3, 5.4.4 Parent: Critical Software Development Process Perspective: Software Engineering In Triggers (IT)Out Triggers (OT)External Inputs (EI) EI1: SW PA Requirements (diag. 26) External Outputs (EO) Software Requirements Analysis R-1 E-40 sec. 5.4.2 SUPPLIER SW Support Spec PICA Spec EI1 Preliminary Design Review E-40 sec. 5.4.3.6 Delivered PDR DP Reviewed PDR DP PDR Data Package PDR Report Reliability and System Analysis Q-80 sec. 3.3.2e System Level Functional Analysis SW RAMS Analysis Higher Level Safety Plan Software Top Level Architectural Design R-2 E-40 sec.5.4.3 SW Prototyping for Critical Components T SW Criticality analysis Use of Petri Nets for dynamic aspects and concurrent feature of TCS SW T