Common Mechanisms of UML

Forward and Reverse Engineering

To forward engineer a use case diagram: 

• Identify the objects that interact with the system 
• Try to identify the various roles that each external object may play
• Make up an actor to represent each distinct interaction role
• For each use case in the diagram, identify its flow of events and its exceptional flow of events 
• Generate a test script for each flow using the flow's preconditions, taking into account the tests initial and post condition state as its success criteria 
• Generate test scaffolding to show each actor that interacts with the use case wherever necessary 
• Actors are either simulated or replaced by a real-world equivalent when they push information to the element or are acted upon by the element 
• Use tools to run these tests whenever needed to release the element to which the use case diagram is assigned 

To reverse engineer a use case diagram: 

• Analyze each actor that interacts with the system 
• For each actor, study how the actor interacts with the system, changes the state of the system, or responds to some event 
• Detect the flow of events in the executable system corresponding to each other 
• Primary flows must be dealt with first. Later alternative paths should be considered 
• Cluster related flows by declaring a corresponding use case 
• Consider modeling variants using extend relationships, and common flows by applying include relationships 
• Represent these actors and use cases in a use case diagram, and establish their relationships 
• The executable and the atomic computations are known as the action states. This is because they are the states of the system that represent the execution of an action