系统分析技术简单介绍

r囧r小猫 2023-07-18 15:28 31阅读 0赞

[上一篇：业务分析][Link 1]

# 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.  
系统分析：一种解决问题的技术，将系统分解成各个组成部分，目的是研究这些组成部分如何有效地工作和交互以实现其目的。

## I/O of System Analysis ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70]

> 回顾业务分析![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 1]

# 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  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 2]  
● 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 ###

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 4]

## 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.  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 5]  
**Relationships - Extends**  
● Why to identify extends relationship?  
A use case is too complicate. Decompose a use case to small use ceses  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 6]  
**Relationships - Uses (or Includes)**  
● Why to identify uses relationship?  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 7]  
**Relationships - Depends On**  
● Why to identify depends on relationship?  
● Any other cases?  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 8]  
**Relationships - Inheritance**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 9]  
**Sub Systems**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 10]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 11]

## 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  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 12]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 13]

## 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 优先考虑用例 ###

#### 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 ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NzUzNzc4_size_16_color_FFFFFF_t_70 14]  
**Readings**  
*System Analysis and Design Methods 7th- Whitten & Bentley*  
○ Chapter 7

[Link 1]: https://blog.csdn.net/qq_39753778/article/details/105024202
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