Appropriate use of UML notations is very important for making a meaningful model

UML Diagram Objects   UML Diagram objects and their usage
Here is an overview of all the nine different kinds of Modeling diagram objects that are wrapped under the heading of the UML.

  • UML Class Diagrams
  • UML Use Case Diagrams
  • UML Object Diagrams
  • UML Sequence Diagrams
  • UML Collaboration Diagrams
  • UML Statechart Diagrams
  • UML Activity Diagrams
  • UML Component Diagrams
  • UML Deployment Diagrams

All these objects are available in Creately and you can try out a demo or take a look at some sample UML Diagrams for more context.

Simple Class

The core element of a UML Class Diagram is the class. This is a solid rectangle contains the class name.

Class Object

A class object in a UML Class Diagram represents an entity of a given system that provides an encapsulated implementation of certain functionality of a given entity. This is a rectangle divided into three compartments. The topmost compartment contains the class name. the middle compartment contains the attributes while the lowest compartment contains the list of operations.


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.


The Interface object found in a UML Class Diagram indicates a set of operations that would detail the responsibility of a class.


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”.

Simple Object

The simple object from the UML Object Diagram is a rectangle which displays the object name. This object name is usually underlined.


The object element from the UML Object Diagram is a rectangle divided into two parts. The top part contains the name of the object, while the second part contains the attributes of the object. Note : This element should not be mistaken with the Class element which is divided into three parts.


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.

Lifeline Notation

The object notation of a UML Sequence Diagram is a rectangle with it’s lifeline (a dashed line) descending from the center of its bottom edge. This element represents the life span of the object during the scenario being modeled.


The object element found in the UML Collaboration Diagram is a rectangle which displays the object name, preceding a colon. The object name is underlined. This shows the objects interacting with each other in the system.


Comment object in a UML Sequence Diagram and UML Activity Diagram is shown in a rectangle with a folded-over corner. To relate the comment to any object on the diagram, the comment has to be connected to the object with dashed lines.


Activation elements in the UML Sequence Diagram are boxes on the lifelines. These are also called the method-invocation boxes, and indicate that an object is responding to a message. It starts when the message is received and ends when the object is done handling the message.

Destroy Object

Destroy object in a UML Sequence Diagram is a X at the bottom of an Activation box. This is a UML convention to indicate an object has been removed from memory.

Message Arrow

Message Arrow in the UML Collaboration Diagram shows the interaction between the commencing object and the destination object.

Initial State

The Initial State from the UML Statechart Diagram is the state of an object before any transitions. For objects, this could be the state when instantiated. The Initial State from the UML Activity Diagrammarks the entry point and the initial Activity State. The notation for the Initial State is a small solid filled circle. There can only be one Initial State on a diagram.

End State

End state from the UML Statechart Diagram marks the destruction of the object who’s state we are modeling. The Activity End in aUML Activity Diagram shows the termination of the activity. The End notation is shown as a circle surrounding a small solid filled circle.


Activity state in a UML Statechart Diagram and UML Activity Diagram marks an action by an object. The notation for this is a rounded rectangle.


Junction state in a UML Statechart Diagram are vertices that are used to chain together multiple transitions. They are used to construct compound transition paths between states. A junction is represented by a small black circle.


Choice state in a UML Statechart Diagram evaluates the guards of the triggers of its outgoing transitions to select only one outgoing transition. The decision on which path to take may be a function of the results of prior actions performed in the same run-to-completion step. A choice pseudostate is shown as a diamond-shaped symbol.

Fork / Join

Fork vertices in the UML Statechart Diagram serve to split an incoming transition into two or more transitions terminating on orthogonal target vertices. The segments outgoing from a fork vertex must not have guards or triggers. Join vertices serve to merge several transitions emanating from source vertices in different orthogonal regions. The transitions entering a join vertex cannot have guards or triggers.

A Fork notation in a UML Activity Diagram is a control node that splits a flow into multiple concurrent flows. This will have one incoming edge and multiple outgoing edges. A join node is a control node that synchronizes multiple flows.This will have multiple incoming edges and one outgoing edge.

Composite State

A composite state in a UML Statechart Diagram is a state that has substates (nested states).


The Object notation in a UML Activity Diagram is an activity node that is used to define the object flow in an activity.


Decision notation in a UML Activity Diagram is a control node that accepts tokens on one or two incoming edges and selects one outgoing edge from one or more outgoing flows.

Flow End

Flow End node in a UML Activity Diagram is a control final node that terminates a flow. It destroys all tokens that arrive at it but has no effect on other flows in the activity. This is a small circle with a X inside.

Signal Receipt

Signal Receipt notation also called the Accept event action in a UML Activity Diagram is an action that waits for a specific event to occur. This is drawn as a concave pentagon.

Signal Sending

Signal Sending in UML Activity Diagram is an action that creates a signal instance from its inputs, and transmits it to the target object, where it may cause the firing of a state machine transition or the execution of an activity.

Activity Partition

Activity Partition in a UML Activity Diagram is either horizontal/vertical swimlane. The partitions are used to separate actions within an activity diagram.


A Component UML Component Diagram represents a modular part of a system. A Component element in a UML Deployment Diagramrepresents a distributable piece of implementation of a system.

Provided Interface

A Provided Interface of a component in a UML Component Diagram describes the services that the component offers to its environment. This is modeled using the lollipop notation.

Required Interface

A Required Interface of a component in a UML Component Diagram declares the services that the component expects from its environment. This is modeled using the socket notation.

Provided Interface & Required Interface with Port

A Provided Interface with Port in a UML Component Diagramspecifies a distinct interaction point between the component and its environment. Ports are depicted as small squares on the sides of components.


A Node element in a UML Deployment Diagram is anything that performs work in the system. This can be either a hardware like personal computers; or a software like the operating system, database server and so forth.


A Device element in a UML Deployment Diagram is a type of node that represents a physical computational resource in a system, such as an application server.

Deployment Specification

A Deployment Specification element in a UML Deployment Diagramis a configuration file, such as an XML document or a text file that defines how an artifact is deployed on a node.

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