Essay on Chapter 5

Chapter 5: Extending the Requirements Models
Use Case Descriptions
Activity Diagrams for Use Cases
The System Sequence Diagram – Identifying Inputs and Outputs
The State Machine Diagram – Identifying Object Behaviour
Integrating Requirements Models
The way the business objects interact with each other in the use case determines how you identify the initiating activity. We refer to those activities as messages between obejcts.
Overview:
Understand the users’ needs, how the business processes are carried out, and how the system will be used to support those business processes.
Use a set of models to to discover and understand the requirements for a new system.
Discovery Activities  Understanding
Two primary objects of functional requirements: use cases and the things involved in users’ work
Use cases are identified by using the user goal technique and the event decomposition technique.
Information storage requirements of a system are documented either with entity-relationship diagrams (ERDs) or with UML domain model class diagrams.
UML system sequence diagrams (SSDs) are introduced to show more information about each use case.
UML state machine diagrams are introduced – help you show more information about domain classes
Use Case Descriptions:
A textual model that lists and describes the processing details for a use case
An actor is a person who uses the system(UML).
An actor is always outside the automation boundary of the system but may be part of the manual portion of the system, but may be part of the manual portion of the system.
How shall the automated system respond to the wants of the actor?
A use case uses a whole sequence of steps to complete a business process.
The use case “create customer account” will have separate flow of activities depending on which actor invokes the use case”. These flow of activities are called SCENARIOS (or USE CASE INSTANCES). Thus, a scenario is a unique set of internal activities within a use case and represents a unique path through the use case.
Scenarios: unique set of internal activities within use cases.
Brief Use Case Descriptions:
Two separate levels of detail: brief description and fully developed description: brief description and fully developed description.
Brief descriptions  add product comment or send message
Fully developed descriptions for  Full shopping cart
Fully Developed Use Case Descriptions:
Use case Descriptions:
1st and 2nd Compartment: Identifies the use cases and the scenarios with the use cases.
3rd: Identifies the event that triggers the use case
4th: Brief description of the use case or scenario (may duplicate the brief description constructed here earlier)
5th: Identifies actors or actors.
6th: Identifies other use case and the way they are related to this use case.
7th: Identifies stakeholders who are interested parties rather than specific actors.
No one in the marketing department create new customer accounts, they perform statistical analysis of the new customers and create marketing promotions.
Sales department is interested in having an easy-to-use and attractive user interface to assure sales aren’t lost because of poor user experience.
8th & 9th: preconditions and postconditions (how does the state of the system react before and after the use case executes). Preconditions – a condition that must be true before a use case begins (what objects must already exist, what information must be available, and even the condition of the actor prior to beginning the use case).
Postconditions: what must be true upon completion of the use case. How new objects are created or updated by the use case and how objects need to be associated.
Form the bases for stating the expected results for the test cases that will be used for testing the use case after it is implemented. For example, in the Create Customer Account use case, it is important to test that a customer record, address record, and account were

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