What is the UML?
UML stands for Unified Modeling Language
The UML is the standard language for visualizing, specifying, constructing, and documenting the artifacts of a software-intensive system
It can be used with all processes, throughout the development life cycle, and across different implementation technologies.
UML Concepts
The UML may be used to:
– Display the boundary of a system & its major functions using use cases and actors
– Illustrate use case realizations with interaction diagrams
– Represent a static structure of a system using class diagrams
– Model the behavior of objects with state transition diagrams
– Reveal the physical implementation architecture with component & deployment diagrams
– Extend your functionality with stereotypes
Putting the UML to Work
The ESU University wants to computerize their registration system
– The Registrar sets up the curriculum for a semester
• One course may have multiple course offerings
– Students select 4 primary courses and 2 alternate courses
– Once a student registers for a semester, the billing system is notified so the student may be billed for the semester
– Students may use the system to add/drop courses for a period of time after registration
– Professors use the system to receive their course offering rosters
– Users of the registration system are assigned passwords which are used at logon validation
Use Cases
A use case is a pattern of behavior the system exhibits
– Each use case is a sequence of related transactions performed by an actor and the system in a dialogue
Actors are examined to determine their needs
– Registrar -- maintain the curriculum
– Professor -- request roster
– Student -- maintain schedule
– Billing System -- receive billing information from registration
Documenting Use Cases
A flow of events document is created for each use cases
– Written from an actor point of view
Details what the system must provide to the actor when the use cases is executed
Typical contents
– How the use case starts and ends
– Normal flow of events
– Alternate flow of events
– Exceptional flow of events
Maintain Curriculum Flow of Events
This use case begins when the Registrar logs onto the Registration System and enters his/her password. The system verifies that the password is valid (E-1) and prompts the Registrar to select the current semester or a future semester (E-2). The Registrar enters the desired semester. The system prompts the professor to select the desired activity: ADD, DELETE, REVIEW, or QUIT.
If the activity selected is ADD, the S-1: Add a Course subflow is performed.
If the activity selected is DELETE, the S-2: Delete a Course subflow is performed.
If the activity selected is REVIEW, the S-3: Review Curriculum subflow is performed.
If the activity selected is QUIT, the use case ends.
...
Use Case Diagram
Use case diagrams are created to visualize the relationships between actors and use cases
Uses and Extends Use Case Relationships
As the use cases are documented, other use case relationships may be discovered
– A uses relationship shows behavior that is common to one or more use cases
– An extends relationship shows optional behavior
Use Case Realizations
The use case diagram presents an outside view of the system
Interaction diagrams describe how use cases are realized as interactions among societies of objects
Two types of interaction diagrams
– Sequence diagrams
– Collaboration diagrams
