Requirements

1. Environment System ECE362 Principles of Design The System Engineering Process Requirements

2. Requirements Overview • This unit overlaps and utilizes the ideas of the previous units, to assemble the metaclasses into requirements supporting structures, emphasizing the HLR Process. • Content: • Requirements versus design • High level requirements (HLR) process • Detail level requirements (DLR) process • Analysis: decomposition of functions, states, systems • Assembling specification documents

3. Customer/Market Needs Available Technologies Requirements-design iteration Design Specification (“Design”) Requirements Specification (“Analysis”) design impacts requirement structure refinement refinement

4. Engineering processes • This section will particularly focus on model-based methodology for representing high level requirements and high level design frameworks.

5. Environment System Requirements (or PDS) • Statements at external boundary of subject system • What we want the system to be or do

6. Environment System Design • Statements about internalphysicalcomponents and theirinteractionrelationships • How we are going to meet requirements

7. Environment System Interfaces • Connect internal components to external components or actors • Help us group attributes and behaviors seen externally

8. Design statement Requirement statement Detailed design statement Detailed requirement statement More detailed design statement More detailed requirement statement Inside vs. outside Design Interfaces Requirements Environment System Detail does not equal design

9. Environment System Inside vs. outside, continued • Reference boundaries • One person’s design is another person’s requirement

10. An SE benefits “sweet spot” • The High Level Requirements (HLR) and High Level Design (HLD) processes require less time and effort than their detailed counterparts. • However, there is typically a very high return on this investment. • Many organizations utilize extensive detailed specifications, but don’t have HLR and HLD specifications. • This means that there is not a unifying framework structure, shared mentally by all concerned, that simplifies and organizes the detailed specifications. • HLR/HLD is a “sweet spot” in the SE process, because it can rapidly begin digging an organization out of problems caused by this lack.

11. Generic HLR Process • Generic (unconfigured) HLR Processes: • Identify Stakeholder (Customer) Needs Process • Identify System Environment Process • Identify Features, Services Process • Identify Use Cases Process • Identify Functions Process • Identify Scenarios Process • Analyze Logical Architecture Process • Repository and Specification Assembly Process (Validation and verification are associated with most of these processes) • Refer to process framework drawings in handouts.

12. Identify stakeholder needs • Stakeholders are people or organizations with an interest (stake) in the system being specified: • Customers • Users • Operators • Maintainers • Company Owners • Regulators • Others

13. Identify system environment • System environment diagram: • Subject System--system whose requirements are to be specified • Actors--interacting systems external to the Subject System • Boundary defines system by defining what it is not--listing the external interactingactors • Often harder than it looks: • Often skipped as “obvious” • Later source of confusion Actor Actor Actor SubjectSystem Actor Actor

14. Identify system environment • Domain diagram identifies relationships between actors that are important to system requirements • Explicitly models “domain knowledge” about the environment • Establishes the semantics of the subject system specification to follow Actor Actor Actor SubjectSystem Actor Actor

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