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

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. Requirements-design iteration
Customer/Market
Needs
Available
Technologies
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. Requirements (or PDS)
Statements at external boundary of subject system
What we want the system to be or do
System
Environment

6. Design
Statements about internal physical components and their interaction relationships
How we are going to meet requirements
System
Environment

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

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

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

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 interacting actors
Often harder than it looks:
Often skipped as “obvious”
Later source of confusion
Actor
Actor
Actor
Subject System
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
Subject System
Actor
Actor

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