Systems Analysis and Integration - 2 Assignments

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CIS320
Systems Analysis and Integration

Week 2 – Extending Requirement Models

Systems Analysis and Design in a Changing World, 6th Edition

Chapter 5

Overview
This chapter focuses on additional techniques and models to extend the requirements models to show more detail
Outline
Use Case Descriptions
Activity Diagrams for Use Cases
The System Sequence Diagram—Identifying Inputs and Outputs
The State Machine Diagram—Identifying Object Behavior
Integrating Requirements Models

Systems Analysis and Design in a Changing World, 6th Edition

Brief Use Case Description

Brief use case description is often a one sentence description showing the main steps in a use case

Systems Analysis and Design in a Changing World, 6th Edition

Fully Developed Use Case Description

Write a fully developed use case description for more complex use cases
Typical use case description templates include:

Use case name
Scenario (if needed)
Triggering event
Brief description
Actors
Related use cases (<<includes>>)
Stakeholders
Preconditions
Post conditions
Flow of activities
Exception conditions

Systems Analysis and Design in a Changing World, 6th Edition

Fully Developed Use Case Description
Use case: Create customer account

Systems Analysis and Design in a Changing World, 6th Edition

UML Activity Diagram for Use Case
Create Customer Account
Note: this shows flow of activities only

Compare with “Flow of Activities” in Use Case Description

Systems Analysis and Design in a Changing World, 6th Edition

System Sequence Diagram (SSD)

A UML sequence diagram
Special case for a sequence diagram
Only shows actors and one object
The one object represents the complete system
Shows input & output messaging requirements for a use case
Actor, :System, object lifeline
Messages

Systems Analysis and Design in a Changing World, 6th Edition

System Sequence Diagram (SSD)
Notation

Systems Analysis and Design in a Changing World, 6th Edition

Message Notation

Systems Analysis and Design in a Changing World, 6th Edition

SSD Message Examples with Loop Frame

Systems Analysis and Design in a Changing World, 6th Edition

SSD Message Examples

Opt Frame (optional)

Alt Frame
(if-else)

Systems Analysis and Design in a Changing World, 6th Edition

Steps for Developing SSD

Identify input message

See use case flow of activities or activity diagram

Describe the message from the external actor to the system using the message notation

Name it verb-noun: what the system is asked to do
Consider parameters the system will need

Identify any special conditions on input messages

Iteration/loop frame
Opt or Alt frame

Identify and add output return values

On message itself: aValue:= getValue(valueID)
As explicit return on separate dashed line

Systems Analysis and Design in a Changing World, 6th Edition

SSD for Create customer account Use case

Systems Analysis and Design in a Changing World, 6th Edition

State Machine Diagram

State machine diagram
A UML diagram showing the life of an object in states and transitions
State
A condition during an object’s life when it satisfies some criterion, performs some action, or waits for an event
Transition
The movement of an object from one state to another state
Action Expression
A description of activities performed as part of a transition

Systems Analysis and Design in a Changing World, 6th Edition

State Machine Diagram (continued)

Pseudo state
The starting point of a state machine diagram (black dot)
Origin state
The original state of an object before transition
Destination state
The state to which the object moves after the transition
Guard condition
A true false test to see whether a transition can fire

Systems Analysis and Design in a Changing World, 6th Edition

State Machine Diagram
for a Printer

Systems Analysis and Design in a Changing World, 6th Edition

Advanced Concept of State Machine: Composite States

State containing other states and transitions
Printer can be On and either Idle or Working

Systems Analysis and Design in a Changing World, 6th Edition

Advanced Concept of State Machine: Concurrent Paths

Multiple paths in composite state
Printer On paths are independent

Systems Analysis and Design in a Changing World, 6th Edition

Steps for Developing State Machine Diagram

Review the class diagram and select classes that might require state machine diagrams

For each class, make a list of status conditions (states) you can identify

Begin building diagram fragments by identifying transitions that cause an object to leave the identified state

Sequence these states in the correct order and aggregate combinations into larger fragments

Review paths and look for independent, concurrent paths

Systems Analysis and Design in a Changing World, 6th Edition

Steps for Developing State Machine Diagram (continued)

Look for additional transitions and test both directions

Expand each transition with appropriate message event, guard condition, and action expression

Review and test the state machine diagram for the class

Make sure state are really state for the object in the class
Follow the life cycle of an object coming into existence and being deleted
Be sure the diagram covers all exception condition
Look again for concurrent paths and composite states

Systems Analysis and Design in a Changing World, 6th Edition

State Machine Diagram for Sale Object

Systems Analysis and Design in a Changing World, 6th Edition

Extending and Integrating Requirements Models

Use cases
Use case diagram
Use case description
Activity diagram
System sequence diagram (SSD)
Domain Classes
Domain model class diagram
State machine diagram

Systems Analysis and Design in a Changing World, 6th Edition

Integrating Requirements Models

Systems Analysis and Design in a Changing World, 6th Edition

Summary

Chapters 3 and 4 identified and modeled the two primary aspects of functional requirements: use cases and domain classes
This chapter focuses on additional techniques and models to extend the requirements models to show more detail
Fully developed use case descriptions provide information about each use case, including actors, stakeholders, preconditions, post conditions, the flow of activities and exceptions conditions
Activity diagrams (first shown in Chapter 2) can also be used to show the flow of activities for a use case

Systems Analysis and Design in a Changing World, 6th Edition

Summary (continued)

System sequence diagrams (SSDs) show the inputs and outputs for each use case as messages
State machine diagrams show the states an object can be in over time between use cases
Use cases are modeled in more detail using fully developed use case descriptions, activity diagrams, and system sequence diagrams
Domain classes are modeled in more detail using state machine diagrams
Not all use cases and domain classes are modeled at this level of detail. Only model when there is complexity and a need to communicate details

Systems Analysis and Design in a Changing World, 6th Edition