Here, we can consider that a car is a class and Ferrari, Mercedes are the objects. An Object Diagram describes the instance of a class. It visualizes the particular functionality of a system. Objects are the real-world entities whose behavior is defined by the classes.
Objects are used to represent the static view of an object-oriented system. We cannot define an object without its class. Object and class diagrams are somewhat similar. The objects are nothing but real-world entities that are the instances of a class. Skip to content. Step 2 The relations of the object must be known before creating the diagram. Step 3 Association between various objects must be cleared before. Step 4 An object should have a meaningful name that describes its functionality.
Step 5 An object must be explored to analyze various functionalities of it. Purpose of Object Diagram It is used to describe the static aspect of a system. It is used to represent an instance of a class.
It can be used to perform forward and reverse engineering on systems. It is used to understand the behavior of an object. It tells us what hardware components exist and what software components run on them. We illustrate system architecture as distribution of software artifacts over distributed targets. An artifact is the information that is generated by system software.
They are primarily used when a software is being used, distributed or deployed over multiple machines with different configurations. Package Diagram — We use Package Diagrams to depict how packages and their elements have been organized. A package diagram simply shows us the dependencies between different packages and internal composition of packages. Packages help us to organise UML diagrams into meaningful groups and make the diagram easy to understand.
They are primarily used to organise class and use case diagrams. Behavior Diagrams — State Machine Diagrams — A state diagram is used to represent the condition of the system or part of the system at finite instances of time.
State diagrams are also referred to as State machines and State-chart Diagrams. These terms are often used interchangeably. So simply, a state diagram is used to model the dynamic behavior of a class in response to time and changing external stimuli. Activity Diagrams — We use Activity Diagrams to illustrate the flow of control in a system. We can also use an activity diagram to refer to the steps involved in the execution of a use case.
We model sequential and concurrent activities using activity diagrams. So, we basically depict workflows visually using an activity diagram. An activity diagram focuses on condition of flow and the sequence in which it happens. We describe or depict what causes a particular event using an activity diagram. Use Case Diagrams — Use Case Diagrams are used to depict the functionality of a system or a part of a system. They are widely used to illustrate the functional requirements of the system and its interaction with external agents actors.
A use case is basically a diagram representing different scenarios where the system can be used. A use case diagram gives us a high level view of what the system or a part of the system does without going into implementation details.
Sequence Diagram — A sequence diagram simply depicts interaction between objects in a sequential order i. We can also use the terms event diagrams or event scenarios to refer to a sequence diagram. Sequence diagrams describe how and in what order the objects in a system function.
These diagrams are widely used by businessmen and software developers to document and understand requirements for new and existing systems. A communication diagram focuses primarily on objects and their relationships. We can represent similar information using Sequence diagrams,however, communication diagrams represent objects and links in a free form.
Timing Diagram — Timing Diagram are a special form of Sequence diagrams which are used to depict the behavior of objects over a time frame. We use them to show time and duration constraints which govern changes in states and behavior of objects.
Interaction Overview Diagram — An Interaction Overview Diagram models a sequence of actions and helps us simplify complex interactions into simpler occurrences. It is a mixture of activity and sequence diagrams.
If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute. We use a rectangle to represent an object in an Object Diagram. An object is generally linked to other objects in an object diagram.
Figure — notation for an Object For example — In the figure below, two objects of class Student are linked to an object of class College. Figure — an object diagram using a link and 3 objects Links — We use a link to represent a relationship between two objects. Figure — notation for a link We represent the number of participants on the link for each end of the link.
We use the term association for a relationship between two classifiers. The term link is used to specify a relationship between two instance specifications or objects. We use a solid line to represent a link between two objects. Notation Meaning Figure — notation for dependency relationship. Class diagrams, component diagrams, deployment and object diagrams use dependency relationships. A dependency is used to depict the relationship between dependent and independent entities in the system.
Any change in the definition or structure of one element may cause changes to the other. This is a unidirectional kind of relationship between two objects. For example — In the figure below, an object of Player class is dependent or uses an object of Bat class.
Figure — an object diagram using a dependency relationship Association — Association is a reference relationship between two objects or classes. Figure — notation for association Whenever an object uses another it is called an association. We use association when one object references members of the other object. Association can be uni-directional or bi-directional. We use an arrow to represent association. For example — The object of Order class is associated with an object of Customer class.
Figure — notation for aggregation Aggregation is a specific form of association. It is an association that represents a part-whole or part-of relationship.
Aggregation occurs when the lifecycle of the contained objects does not strongly depend on the lifecycle of container objects. Figure — an object diagram using aggregation For example — A library has an aggregation relationship with books. Library has books or books are a part of library. The existence of books is independent of the existence of the library. We use a hollow diamond on the containing object with a line which joins it to the contained object.
Composition — Composition is a type of association where the child cannot exist independent of the other. Figure — notation for composition. Composition is also a special type of association. It is also a kind of parent child relationship but it is not inheritance.
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