System Development - Seminar 5

Use Cases

Traditional way of capturing functional requirements of a system. Includes business rules and system descriptions, details how end-users can interact with a system, and usually done up front and at the start of requirements definition stage of development.

User Goal Technique

Method of identifying use cases. Focuses on goals of user when interacting with new system

Events decomposition technique

More comprehensive method of identifying use cases. User isn’t the focus up front. Looks at identifying all required business events in a system.

Step 1 of User Goal Technique

Identifying all users associated with Use Case

Step 2 of User Goal Technique

Classify them (e.g., functional roles, organisational roles)

Step 3 of User Goal Technique

Think about what Use Case should be

Step 4 of User Goal Technique

Find duplicates

Step 5 of User Goal Technique

Identify users with the same needs

Step 6 of User Goal Technique

Review Use Case with users

Step 1 of Event Decomposition

Think about the things that need to happen in a system at a particular time

Step 2 for Event Decomposition

Name a use case for each event

Step 3 for Event Decomposition

Think about the types of events that occur and find the one that actually affect the system

Step 4 of Event Decomposition

Tracing a sequence of transactions resulting in many events

External events

Initiated by an external agent outside system (e.g., “customer pays bill”)

Temporal events

Events that occur after reaching a certain point in time (e.g., time to send late notices)

State events

Occurs when system reaches a particular state

Actor

Person, software entity, department, or organisation that initiates functionality provided by Use Case (e.g., bank manager)

Primary Actor

Using the system to achieve their goal

Secondary Actors

System needs assistance from them to achieve main goals

Association

Indiciates Actor makes use of functionality in a Use Case. Line between Actor and Use Case with no arrow heads

System boundary

Defines the scope of the system. All the use cases associated with project requirements exist within this

Include relationships

Use Case can be used or inserted into another use case. Can also be reused across multiple use cases.

Extends relationship

Adds functionality to parent use case. Contains optional behaviour for the system. Arrow head points towards parent use case

Generalisation relationship

Tries to optimise model by puting common parts of use cases into a higher use case that never gets called by actor. Child inherits general behaviour from this and adds its own special behaviour based on use case

CRUD

Create, Read, Update, Delete. Used to help validate, refine, or cross-check Use Cases.