What is an Object Diagram

Various objects are used to form an object diagram. There are two significant elements in the object diagram. The first one is the object itself, and the second one is linked (used to connect objects). They both contribute to make the object diagram. These diagrams can also be drawn for “Forward and Reverse Engineering.

Any object can be an instance of a specific moment in Execution time, includes data values and objects. It appears as a print of a comprehensive state of the system. Thus this diagram incorporates their relationship and objects. It can be viewed as a particular case of the communication diagram and the class diagram.


It is mainly used to display examples of the data structures. The primary goals of the object diagram are enlisted as below:

  • You may design a class diagram to define the system’s structure and, after that, design the set of these diagrams as the test cases to authenticate the completeness and accuracy of a class diagram.
  • You may draw an object diagram to find facts about particular links and their model elements, or to depict particular classifier examples that are needed.
  • It facilitates reverse engineering and forward engineering.
  • Practically, it is applied to grasp the relationship and object behavior.
  • It is applied to represent a static perspective of the system.
  • It is also used to get an instance of the system.

Flash of Object Diagram

The object diagram displays the relationship between the objects in the system, defined classes, and the instantiated classes. Sometimes the class diagrams design the recursive relationship or gets complicated, which are beneficial to determine the small fragments of the system. The most elegant way to show what the object diagram view like is to define an object diagram borrowed from the reciprocal class diagram.

Notation of Object Diagram

Object Name

An object can be exemplified same as a rectangle, that shows a name from an object and object’s class underlined in addition to division with the colon.

UML Object Diagram

Object Attributes

Just like the class diagram, you are capable of enlisting the object attributes in a insolate compartments. But, unlike the class diagram, object attributes must have values authorized for them.

UML Object Diagram


Links gravitate to be attached to associations. Anyone can evoke the link during the usage of lines employed in the class diagrams.

UML Object Diagram

Drawing of Object Diagram Structure

Without messages, any communication diagram is called an object diagram, and the relation between the objects is known as links. These diagrams should be an authentic instantiation of the static type of class diagram. Objects should have links, and classes between objects should be association instances between classes. It can be applied as an immediate consistency check. For doing this, you can create the object diagram with the help of the following steps:

  • Identify the structure we’d wish to design. A structure represents some behaviors and functions of the system’s part. We are developing that outcomes form the interfaces, interaction of class society, or other things.
  • For every structure, identify the interfaces, classes, and other components that engage in this kind of collaboration; discover the relationship between these things also.
  • Take a scenario that can collaborate with this structure. Freeze this scenario at a particular time, and deliver all the objects that cooperate in this mechanism.
  • For increasing the understandability of this scenario, disclose the attribute values and the state of all such objects.

Drawing of Object Diagram

  • Every object that presents in a system must be inspected before starting the drawing of an object diagram.
  • Before start designing an object diagram, the relationship among objects should be endorsed.
  • An association relation between the entities should be cleared.
  • To illustrate various functionalities of an object, a valid name must be assigned.
  • Various objects should be inspected to understand their functionality.

Application Areas of Object Diagram

There are so many areas, and fields, where these diagrams can be applied efficiently. Some of the essential areas are as follows:

  • Forward Engineering
  • Reverse Engineering
  • To create a model of the system.
  • To design complicated data structures.
  • To realize a system from the functional perspective.


The following illustrates that one object displays the robot, i.e., r, instance ‘r’ is moving currently. Instance ‘r’ has a connection link with ‘w,’ which represents the robot’s world design abstraction. This object can have a connection link to the multiple objects composed of element instances that show entities that a robot has not assigned yet in this world view but identified. These components remarked as the global state of a robot.

Instance ‘w’ is connected to two of the instances at this moment. One instance is displayed with their connection links to 1 door object and 3 walls. All of these walls are remarked with their current scope and also posted linked to their adjacent walls. In conclusion, the robots have identified this area, which has 3 sided walls and one door.

UML Object Diagram

Difference between Class Diagram and Object Diagram

Some primary differences between the class diagram and object diagram are as follows:

S. No.                    Class Diagram                    Object Diagram
1. It defines the static perspective of the system. It depicts the actual behavior of the system
2. Dynamic changes are not captured in the class diagram. Runtime changes are included in the object diagram
3. The object behavior is not employed in the class diagram. Objects are the instances of the class.
4. Data values and attributes are not captured in this diagram. Object diagram encompasses the data values and attributes of instances.

Pin It on Pinterest

Share This