S Y S T E M S E N G I N E E R I N G
S Y S T E M S E N G I N E E R I N G Definitions The systems engineering process includes the following four fundamental activities. Requirements Analysisis the process of determining what our system has to do, how well it has to do it ,and under what conditions and in what environments must the mission be performed. This is the first step in the Systems Engineering Process. Requirements come from various sources including operational requirements documents (ORDs), concepts of operations and through discussions with the user regarding the mission to be performed. A well written requirement is understandable, unambiguous, comprehensive, complete, and concise. Requirements analysis includes the definition of both system functions and the performance associated with those functions. Functional Analysis/Allocation is the process of defining the product in terms of function and performance. Through functional analysis and allocation the designer comes to understand the logical construct of the system ,i.e.in what order the functions must be performed and what level of performance is required for each function. Functional analysis and allocation generally starts with the decomposition of top level functions identified during requirements analysis into lower level functions and then the allocation of performance requirements to each of the lower level functions. The result of this analysis, is often called the Functional Architecture.
S Y S T E M S E N G I N E E R I N G Definitions • Design Synthesisis the process of describing the system or product in physical terms. Whereas in functional analysis the objective was to describe the product in functional terms, we are now developing the physical elements which will make up the system that is actually built. This physical description is often called a physical architecture. The Physical Architecture is the basic structure for generating the specifications and baselines and it also forms the product elements portion of the WBS. • Systems Analysis & Control evaluates alternative approaches to satisfy technical requirements and program objectives, and provide a rigorous quantitative basis for selecting performance, functional, and design requirements.
S Y S T E M S E N G I N E E R I N G This diagram shows the essential steps required to accomplish the four activities within the systems engineering process. System Analysis & Control (Balance) • Process Input • Customer Needs/Objectives/Requirements • Missions • Measures of Effectiveness • Environments • Constraints • Technology Base • Output Requirements for Prior • Development • Program Decision Requirements • Requirements Applies Through • Specification • Requirements Analysis • Analyze Missions & Environments • Identify Functional Requirements • Define/Refine Performance & Design Constraint Requirement • Trade-Off Studies • Effectiveness Analyses • Risk Management • Configuration Management • Interface Management • Data Management • Performance Measurement • SEMS • TPM • Technical Reviews Requirements Loop • Functional Analysis/Allocation • Decompose to Lower-Level Functions • Allocate Performance & Other Limiting Requirements to All Functional Levels • Define/Refine Functional Interface (Internal/External) • Define/Refine/Integrate Functional Architecture Design Loop Related Terms: Customer = Organizations responsible for Primary Functions Primary Functions = Development, Production/Construction, Verification, Deployment, Operations, Support, Training, Disposal System Elements = Hardware, Software, Personnel, Facilities, Data, Material, Services, Techniques • Synthesis • Transform Architectures (Functional to Physical) • Define Alternative System Concepts, Configuration • Items & System Elements • Select Preferred Product & Process Solutions • Define/Refine Physical Interfaces (Internal/External) • Process Output • Development Level Dependent • Decision Data Base System/Configuration item • Architecture • Specifications & Baselines