An Object diagram falls under the structural diagramming family. An Object diagram is an instance of a Class diagram that shows a complete or a partial view of the structure. This type of diagram displays instances of classifiers and links (instances of associations) between them.


An Object diagram is usually used in the early phases of a project to model examples that show a possible snapshot of the system execution, for example, what the system can look like at some point in time. Additionally, it focuses on the attributes of a set of objects and helps to analyze how these objects relate to each other.


An Object diagram can be used to:

  • represent a class instance
  • describe the static aspect of the system
  • understand the behavior of a particular object
  • analyze object relations
  • perform forward and reverse engineering on chosen systems.


Object diagrams are valuable because they:

  • can be used to model test cases in order to validate the Class diagram
  • support the investigation of requirements by modeling examples from the problem domain
  • examine a specific iteration of a general system
  • later in the project, model test cases to see whether the created Class diagram is correct and complete
  • allows users to get a high-level overview of the system.

Example of an Object diagram

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