UML Tutorial | UML Diagrams | Introducing Types of UML Diagrams

UML stands for Unified Modeling Language. It is a language for creating models. UML is a rich language to model software solutions, application structures, system behavior and business processes. UML is a modern approach to modeling and documenting software. In fact, it’s one of the most popular business process modeling techniques. 

A UML diagram is a diagram based on the UML (Unified Modeling Language) with the purpose of visually representing a system along with its main actors, roles, actions, artifacts or classes, in order to better understand, alter, maintain, or document information about the system.

UML is not a programming language, it is rather a visual language. It is a way of visualizing a software program using a collection of diagrams. We use UML diagrams to portray the behavior and structure of a system. UML helps software engineers, businessmen and system architects with modelling, design and analysis. Mainly, UML has been used as a general-purpose modeling language in the field of software engineering.

Types of UML Diagrams:

There are several types of UML diagrams and each one of them serves a different purpose. Diagrams in UML can be broadly classified as: Structural UML diagram and Behavioral UML diagram

Structural Diagrams: 

Structural UML diagrams, as the name would suggest, show how the system is structured. It depict the structure of a system or process.

Structural Diagrams include: Component Diagrams, Object Diagrams, Class Diagrams and Deployment Diagrams.

Behavior Diagrams: 

Behavioral diagrams describe the behavior of the system, its actors, and its building components. They describe how the objects interact with each other to create a functioning system.

Behavior diagrams show the dynamic behavior of the objects in a system, which can be described as a series of changes to the system over time

Behavior diagrams include: Use Case Diagrams, State Diagrams, Activity Diagrams and Interaction Diagrams.

Structural Diagrams:

Class Diagram: 

The most widely used UML diagram is the class diagram. It is the main building block of any object-oriented solution. Class diagrams are the backbone of almost every object-oriented method, including UML. They describe the static structure of a system.

It shows the classes in a system, attributes, and operations of each class and the relationship between each class. Class UML diagram is the most common diagram type for software documentation. It is a central modeling technique that runs through nearly all object-oriented methods.

Behavior Diagrams:

Use Case Diagrams: 

Use case diagrams model the functionality of a system using actors and use cases. They are widely used to illustrate the functional requirements of the system and its interaction with external agents (actors). Use case diagrams give a graphic overview of the actors involved in a system, different functions needed by those actors and how these different functions interact.

 

Activity Diagrams: 

In software development, activity diagram is generally used to describe the flow of different activities and actions. Activity diagrams illustrate the dynamic nature of a system by modeling the flow of control from activity to activity.

Activity diagrams represent workflows in a graphical way. They can be used to describe the business workflow or the operational workflow of any component 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.

 

Sequence Diagram: 

A sequence diagram simply depicts interaction between objects in a sequential order i.e. the order in which these interactions take place.

A sequence diagram, sometimes referred to as an event diagram or an event scenario, shows the order in which objects interact. 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.

Difference between DFD and UML diagram:

A DFD illustrates how data flows through a system, while UML is a modeling language used in object oriented software design. UML diagrams mainly represent the structural view and the behavioral view of a system. 

 

A data flow diagram describes how information is shared (routed) through the various elements of the system. UML use case and sequence diagrams are mostly used to illustrate the functional requirements of a system in the object-oriented approach.

 

UML is an object modelling system while DFD are data modelling systems. In object models, we have systems based on object orientation termed to as blue prints in a system. They include; class diagrams, associations among the classes created and properties of these classes among others. On the other hand, data models encompass units in the stage of database. They are concerned with table schema that is, comparing a collection of tables.