UML Use Case Diagram objects and their usage
This is an overview of all the UML Use Case Diagram objects that you will use when drawing class diagrams and design patterns. All these objects are available in Creately and you can try out a demo or take a look at some sample UML Use Case Diagrams for more context.
A package object in a UML Class and Use Case Diagram provides the ability to group together classes and/or interfaces that are either similar in nature or related. Grouping these design elements in a package element provides for better readability of UML diagrams, especially complex diagrams.
Actor in a UML Use Case Diagram is any entity (person, organization or external system) that performs a role in one given system. In a use case diagram, an actor interacts with a use case. For example, for modeling a reservation system, a passenger entity represents an actor in the application. Similarly, the ticket clerk who provides the service at the counter is also an actor.
A use case in a UML Use Case Diagram gives a visual representation of a distinct business functionalities in a system. For example, for modeling a clinic system, the use cases will be "Make appointment" and "Perform medical tests".
A system in a UML Use Case Diagram is a rectangle spanning all the use cases in the system that defines the scope of your system. Anything within the box represents functionality that is in scope and anything outside is not. Note that the actors in the system are outside the system.