What is UML (Unified Modeling Language) and UML Diagrams?

What is UML

What is UML (Unified Modeling Language) and UML Diagrams?

UML (Unified Modeling Language) Detailed Overview

UML, an acronym for Unified Modeling Language, is really a structured modelling language consisting of an interconnected set of diagrams designed to help system and software developers define, imagine, build and document software applications, as well as process models or other non-software systems.

UML is a set of best engineering practices that have proven effective in modelling large and complex systems. UML is just a very important step in the development of object-oriented software and software creation processes.

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UML was formed as a result of the confusion surrounding the production and documentation of software. Across the 1990s, there have been varieties of different ways to view and record software systems.

The need emerged for a more cohesive way to visually reflect these structures and as a result, in 1994-1996, three software engineers working at Rational Software created the UML.

This was eventually introduced as a standard in 1997 and has since remained the standard, receiving just a few other changes.

As the strategic importance of software grows for many businesses, the industry is looking for strategies to optimize software development, boost quality, and reduce costs and time-to-market.

These methods include component technology, visual programming, patterns, and frames. Businesses are now searching for methods to handle the complexity of processes as they grow in reach and size.

In general, they recognize the need to solve recurrent architectural problems such as distribution channels, correlation, duplication, security, load balancing, and low latency.

Both of these people are involved in various facets of the program, and each of them needs a particular level of detail.

For example, a coder needs to understand the design of the system and be able to translate the design to low-level code.

On the other hand, a technical writer is interested in the actions of the system as a whole and wants to understand how the process functions.

UML aims to include a vocabulary that is so descriptive that all stakeholders will benefit from at least one UML diagram.

Why we use UML in Software Engineering?

UML was mainly used as a general-purpose modelling language in the software engineering field. After all, a variety of business operations or workflows have now been documented.

For example, activity diagrams, a form of UML diagram, can be used to replace flowcharts. They also provide a more structured way of modelling workflows and a wider set of choices to added advantage and performance.

  • Provide a prepared-to-use, expressive visual modelling language for users to develop and share meaningful models.
  • Provide extensibility and expertise mechanisms to broaden core concepts.
  • Be independent of specific programming languages and development processes.
  • Provide a formal framework for understanding the language of modelling.
  • Encourage the growth of the market for OO tools.
  • Incorporate the recommended method.

What are the major types of UML diagrams?

Below are many types of UML diagrams, each of which serves a particular purpose, regardless of whether it is built before or after implementation (as part of the implementation process).

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The behavioural UML diagram and structural UML diagram are also the two broadest categories that encompass all other forms.

As the name suggests, some UML diagrams aim to explain and represent the structure of the system or operation, while others define the behaviour of the system, its actors, and its building components. The different styles are divided into the following:

Major Concepts used In UML diagrams

  1. Class –A class in UML diagrams tells the basic idea of the structure and functions of an object used in class.
  2. Objects –Objects help us break down large structures and allow us to modulate our behavior. Modularity allows us to break our system into understandable components so that we can construct our system piece by piece. The object is the basic unit (building block) of a device used to represent the individual.
  3. Inheritance –Inheritance is a process by which child/Subclasses inherit the characteristics of their parent/Superclasses.
  4. Abstraction –It is the process by which implementation details are hidden from the user end.
  5. Polymorphism –It is the method by which functions or entities are to show themselves in more than one foam.

Structural UML Diagram

Catch the static feature or structure of the device. Structure Diagrams include Unit Diagrams, Object Diagrams, Category Diagrams, and Deployment Diagrams.

  1. Class Diagram – The class diagram is by far the most commonly used UML diagram. This is the key component of all object-oriented software systems. We use class diagrams to represent the static function of the model by displaying the classes, methods, and attributes of a system. Class diagrams also enable us to define the relationship between different classes and objects.
What is UML
What is UML

This is an example of a Class Diagram in which the user chooses software classes from the case study, and named in the top rectangle i.e. Fix, Operations, etc. in the second rectangle, there are attributes such as date and name or ID, in the third rectangle there are function/methods used to make code at the end and implement software.

  1. Composite Structure Diagram – We choose composite structure diagrams to reflect the inner structure of the class and its points of contact with other components of the process. The composite structure diagram describes the relationship between the parts and their specification, which defines how the classifier (class, component, or deployment node) behaves. They reflect the internal structure of a hierarchical classifier that uses parts, sockets, and connectors. Collaborations can also be modelled using composite structure diagrams. They are close to class diagrams except that they represent individual parts to depth compared to the overall class.
What is UML
What is UML

This is an example of a Composite Structure Diagram.

Object Diagram – The Object Diagram can be referred to as a snapshot of the device instances and the relationship that occurs between them.

Because object diagrams represent actions when objects have been instantiated, we are able to analyze the behaviour of the system at a given moment.

The object diagram is similar to the class diagram in that it displays the class instances in the method. We represent the actual classifiers and their relationships that make use of class diagrams.

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At the hand, the Object Diagram represents unique instances of classes and relationships between them at a time point.

What is UML
What is UML

This is an example of an Object diagram

Component Diagram – Unit diagrams are used to describe how the physical elements of the device have been arranged. We use them to model the specifics of the implementation.

Component Diagrams represent the structural relationship between the elements of the software system and enable us to understand whether functional requirements have been addressed by the planned development.

Component diagrams are becoming important to use when designing and building complex structures. Interfaces are used by system elements to communicate with each other.

What is UML
What is UML

This is an example of an Object Diagram

Deployment Diagram – Deployment Diagrams are used to describe hardware devices and their software. This shows us what hardware components exist and what software components operate on them.

They explain system architecture as a set of software objects over distributed goals. The artefact is the information created by the machine program.

They are mainly used since the software is being used, distributed, or distributed over several machines with different configurations.

What is UML
What is UML

Package Diagram – We use Package Diagrams to demonstrate how packages and their components have been arranged.

The package diagram clearly shows us the dependencies between the various packages and the internal package composition.

Packages help us organize UML diagrams into coherent classes and make the diagram simple to understand. These are mainly used to organize a class and use case diagrams.

What is UML
What is UML

Behavioural UML Diagram

Catch the complex aspects or actions of your system. Behaviour diagrams include using case diagrams, condition diagrams, operation diagrams, and interactive diagrams.

  • Activity Diagram
  • Use Case Diagram
  • Interaction Overview Diagram
  • Timing Diagram
  • State Machine Diagram
  • Communication Diagram
  • Sequence Diagram

State Machine –Diagrams the state diagram is used to describe the status of the system or part of the system at finite times.

It is a behavioural diagram, and it describes a behaviour that uses finite state transitions. State diagrams are sometimes referred to as System diagrams and State diagrams.

Such concepts are also used interchangeably. Simply put, a state diagram is used to show the dynamic behaviour of a class in response to time and changing visual input.

What is UML
What is UML

Activity Diagrams – We use activity diagrams to display the flow of control in the system. The activity diagram can also be used to refer to the steps involved in the implementation of the use case.

We are modelling sequential and parallel tasks using task diagrams. In addition, essentially, we visually represent workflows using the activity diagram.

The activity diagram focuses on the state of the process and the order in which it happens. We explain or display what triggers a specific event using an activity diagram.

What is UML
What is UML

Use Case Diagrams Using Case Diagrams to represent the features of a system or part of a system. They are commonly used to demonstrate the functional specifications of the system and its relations with external agents (actors).

The use case is essentially a list of various situations where the device should be used. The use case example gives us a high-level view of what the system or part of the system does without getting into the particulars of the implementation.

What is UML
What is UML

Sequence Diagram – A sequence diagram essentially represents the interaction between events in sequential order, i.e. the order in which such interactions take place.

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The term event diagrams or event scenarios may also be used to refer to a sequence diagram. Sequence diagrams explain how and in what order the artefacts in the system operate.

Such diagrams are commonly used by entrepreneurs and software developers to record and understand the specifications of new and existing systems.

What is UML
What is UML

Communication Diagram – The Communication Diagram is used to represent sequential messages exchanged between objects.

The contact diagram focuses mainly on objects and their relationship. Similar information can be represented using sequence diagrams, but communication diagrams depict objects and connections in a free form.

What is UML
What is UML

Timing Diagram – Timing Diagram is a special type of sequence diagrams used to represent the actions of events over a period. We use them to demonstrate time and length constraints that control changes in object states and actions.

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Interaction Overview Diagram – Interaction Overview Diagram models a series of actions and allows us to simplify complex interactions with simpler occurrences. It is a combination of activity and sequence diagrams.

What is UML
What is UML

What are some tools used for making UML diagrams?

  • Paper and pen– It is the no-brainer. Pick up a paper and a pen, open a UML cheat sheet from the internet, and start drawing any sort of diagram you like.
  • Online tools – There are a variety of online tools that can be used to create a UML diagram. Many of them offer free trials or a limited number of top-tier diagrams. When you are searching for a long-term solution for drawing UML diagrams, it is usually more useful to buy a paid subscription for one of the applications.
  • Free Online Tools – They are doing pretty much the same thing as the paying ones do. The biggest difference is that paying people often provide tutorials and ready-made models for different UML diagrams. Draw.io is a fantastic free resource.
  • Desktop application – Microsoft Visio is a standard software framework for UML diagrams and almost every other kind of diagram. It provides advanced options and features. The only downside is that you have to pay for it.
  • Visual Paradigm– this is the perfect and professional tool for making UML diagrams used by almost 90% developers for making software documentation and the examples in this articles are made by using Visual Paradigm and draw.io an online tool.


Time is money and so It is very important to design software in the given time period by every developer. Therefore, we need to make a UML diagram for this purpose to make sure that when and how we can design software for some clients.

It is a most important course in the degree of Software engineering and Computer Science so all the students need to learn this course by using this article, which tells all of us how it is useful and how to make these diagrams.

As you may have found, and use a UML diagram to chart processes and structures can be very beneficial. The downside is that it may seem difficult to draw one at first.

Nonetheless, once you start talking about UML specifications, you can get a better understanding of the method or framework, which you are mapping.

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