What Is Systems Analysis
● Systems analysis - a problem-solving technique that decomposes a system into its component pieces for the purpose of studying how well those component parts work and interact to accomplish their purpose.
系統分析：一種解決問題的技術，將系統分解成各個組成部分，目的是研究這些組成部分如何有效地工作和交互以實現其目的。
I/O of System Analysis
回顧業務分析
Use Case Modeling
Use Case Modeling
● User Centered development - a process of systems development based on understanding the needs of the stakeholders and the reasons why the system should be developed.
user story
● Use Case Modeling - the process of modeling a system’s functions in terms of business events, who initiated the events, and how the system responds to those events.
● Use Case Diagram - a diagram that depicts the interactions between the system and external systems and users. In other words, it graphically describes who will use the system and in what ways the user expects to interact with the system.
● Use Case Narrative - a textual description of the business event and how the user will interact with the system to accomplish the task.
Use Case Diagram
A Simple Use Case Diagram
● Use Case - a behaviorally related sequence of steps (a scenario), both automated and manual, for the purpose of completing a single business task
● Actor - Anything that needs to interact with the system to exchange
information
○ Primary business actor
○ Primary system actor
○ External server actor
○ External receiver actor
● Relationships
○ Association - a relationship between an actor and a use case in which an interaction occurs between them
■ Imitated by the actor
■ Between use case and an external server or receiver actor
Student Information System - Context Diagram
A New Requirement
● As an academic affairs officer, I want a daily report listing which courses have been closed to enrollment (no open seats available) and which courses are still open so that I can decide if I need to adjust courses schedule.
Relationships - Extends
● Why to identify extends relationship?
A use case is too complicate. Decompose a use case to small use ceses
Relationships - Uses (or Includes)
● Why to identify uses relationship?
Relationships - Depends On
● Why to identify depends on relationship?
● Any other cases?
Relationships - Inheritance
Sub Systems
Use Case Narratives
● Basic information - id, name, description, etc.
● Priority
● Actors
Business actors, System actors, External actors
● Precondition
● Trigger
● Typical Course Events
● Alternate Courses
● Conclusion
● Postconditions
● Business Rules
● Implementation Constraints and Specifications
● Assumptions
● Open Issues
● SAUC-001: Apply a course
Use Case Management
The Process of Use Case Modeling
● Identify Business Actors
● Identify Business Requirements Use Cases
● Construct Use Case Model Diagram
● Document Business Requirements Use Case Narratives
Prioritizing Use Cases 優先考慮用例
Identifying Use Case Dependencies
○ Focus on Depends on relationship in your use case diagram
○ Extract the depends on relationships to a Dependency Diagram
■ Graphical depiction of the system’s events and their states enhances understanding of system functionality.
■ Helps identify missing use cases.
■ Helps facilitate project management by depicting which use cases are more critical.
Ranking and Evaluating Use Cases
○ Significant impact on the architectural design.
○ Easy to implement but contains significant functionality.
○ Includes risky, time-critical, or complex functions.
○ Involves significant research or new or risky technology.
○ Includes primary business functions.
○ Will increase revenue or decrease costs.
Use Case Ranking and Priority Matrix
Readings
System Analysis and Design Methods 7th- Whitten & Bentley
○ Chapter 7