6 Oct 2011
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USE CASE MODELING
REVIEW
Requirement Specification
– Data Dictionary and Context Diagram, List of Natural Statements
(Requirement Set), Problem Statement
○They use natural language (rich, nuanced, not constrained), English
○Challenging to communicate requirements precisely and
unambiguously ......
Use Case Modeling
– Use Case Diagram, Activity Diagram, Use Case Description
– How the system shall behave to satisfy the user requirements
○They use UML (Unified Modelling Language)
Facilitate communication between Analysts, Designers, Clients,
Managers, etc
Amenable to standard methods of analysis
Useable throughout the software life cycle
Context Diagram
– Shows the boundaries of the system and the category of users expected to
interact with the system (Actors)
Use Case Diagram
– Specifies of the “pieces” of system functional behaviour that would satisfy
the itemized of user requirement
– Each major/coherent functional behaviour “piece” is called a Use Case
– It is the process of moving “ what the user wants from the system” to “how
the system shall behave to satisfy it”
○There is no reference to the internal structure of the system
It doesn’t care about how the system should be made
Use Case
Example: System Sequence of Actions
1) The customer submit a completed payment form
2) The System validates the customer’s payment information
3) The System submit the payment request to the financial institution
4) The System notifies the Costumer with a “Successful Payment”
5) The Use Case ends
Use Case Scenarios
– A Scenarios is an complete path if execution through the entire use case
– A scenario is a instance of the use case
○Happy day scenarios is when it results in the successful realization of
the post condition (function)
○An Exception Scenarios results in an exception state. The function is
not achieved
Use Case Flow versus Scenarios
– Flow of a use case are like the network of roads connecting two cities
– Scenarios of a use case are like the possible itineraries between two cities
Why do we need scenarios?
– Ask Melanie