UML Concepts

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