What is a UML Diagram? - An Easy and Comprehensive Guide
What is a UML Diagram?
A UML diagram shows the unified visual presentation of the UML (Unified Modeling Language) system with the aim to let developers or business owners better understand, analyze and undertake the structure and behaviors of their system. To be more simple, such diagram is very similar to blueprints used in construction building projects. So far, the UML diagram has become one of the most common business process modeling tools and is doing well for large and complex projects. UML is also highly significant to the development of object-oriented software with more clear and easy notations.
Why Use UML Diagrams?
UML diagramming has many benefits for both software developers and businessman, and the most key advantages are:
Problem-Solving - Enterprises can improve their product quality and reduce cost especially for complex systems in large scale. Some other real-life problems including physical distribution or security can be solved;
Improve Productivity - By using the UML diagram, everyone in the team is on the same page and lots of time are saved down the line;
- Easy to Understand - Since different roles are interested in different aspects of the system, the UML diagram offers non-professional developers, for example, stakeholders, designers, or business researchers, a clear and expressive presentation of requirements, functions and processes of their system.
UML Diagram Key Usages
The diagram can be used in many different fields including software engineering or business processes to strengthen efficiency.
Draft the System - In this case, the UML diagram is used by the development team to discuss the outlines and structure the overall system. This may include the forward design and the backward design for different activities, roles, actors, and so on;
Visualize Programming Language - Different types of UML diagrams in a certain system can be translated into code directly to save time for software or related application development;
Business Analysis - In reality, the UML diagram can also be used to analyze the business sales pathway in order to improve customer service;
What are the Types of UML Diagrams?
The two most main categories of UML diagrams are the Structure UML diagram and the Behavior UML diagram. Furthermore, 13 sub-types of UML diagrams are divided into these two groups and each one of them has a different purpose. Now let's check out all of them in more details as shown below. You can also click on them to see more and download these examples for free.
These diagrams show different objects and the static structure of the system. The elements in a structure diagram may include abstract and some other related implementation concepts. This category has six sub-types:
- Class diagram
- Composite Structure diagram
- Object diagram
- Component diagram
- Deployment diagram
- Package diagram
It is the most widely used UML diagram sub-category. The Class diagram is the building block of all object-oriented software systems. Users can depict the static structure and identify classes relationship of a system by checking system's classes and attributes. Each class has three basic elements: the class name at the top, the class attributes in the middle, and the class behaviors at the bottom. In reality, you can create classes such as "Sales Account" or "Online User" in business systems, or "Teacher" and "Student" in academic systems.
Composite Structure Diagram
Composite structure diagrams are used to show the internal structure, the behaviors of classifiers, and the relationships between classes in a system. The composite structure type is similar to Class diagrams but the former ones represent more detailed individual parts rather than the whole system structure. Object Diagram
Object diagrams can be considered as the screenshot of the instances and their internal relationships in a specific system. By using such diagrams, developers can be able to analyze the operations of the system at a particular instant, and check their abstract structure. Furthermore, the relationship between a Class and an Object in software development can be described as the relationship between, for example, the class "Food" and the brand "KFC" or the general class "User" and a specific username called "David" or what else.
Component diagrams are used to show in what way the physical components in a system is organized. Normally, developers use the Component Diagram to check out implementation details, break down the system into smaller parts, depict the structural relationship between system elements especially in the case of large-scale complex projects with more advanced technologies.
Deployment diagrams are generally used to show users the visual relationship between software and hardware. A sample Deployment diagram in the software development field has two main parts: Nodes (basically different kinds of servers) and Artifacts (normally client or database schema). Nodes host the Artifacts, while different types of Artifacts operate on Nodes.
In general, Package diagrams are used to depict how packages and their elements are organized into meaningful groups in a system. More specifically, Package diagrams can be considered as a structure that includes many deployment diagrams with nodes and artifacts. So far, package diagrams are used to organize the Class and Use Case diagrams.
These diagrams display the dynamic behaviors or in other words, what should happen in a system. For example, the way that objects interact with each other, or a set of changes to the system over a certain period. This category has seven sub-types:
- State Machine diagram
- Activity diagram
- Use Case diagram
- Sequence diagram
- Communication diagram
- Timing diagram
- Interaction Overview diagram
State Machine Diagrams (State Machines or State-chart Diagrams)
Such UML diagrams are used to represent the condition of the system, the dynamic action (different states) of a class in response to a particular time based on internal or external factors. A real-life example of the State Machine diagram could be playing Poker cards. The final result (different states) of the game can be different based on players' specific strategies.
Activity diagrams are used to illustrate the interconnected flow of different activities and actions (both in sequential form or in parallel type) in a system, and to display the steps involved in the execution of a use case. This type of UML diagram is widely used both in business modeling process and software development.
Use Case Diagrams
A Use Case diagram can be regarded as a good starting point for discussing project key actors and processes without going into too many implementation details. This UML diagrams is also the most popular type of the Behavioral UML diagram category, and is used to analyze the functionality (the use cases) and the interactions with different types of agents (actors) of a system. For business cases, enterprises may use such diagrams to check out the customer order system by monitoring the stock, product quality and so on. For daily life cases, Use Case diagrams are similar to the Hot Sale product list of your local supermarket. You know the product name and its prices according to the list when making your purchasing decision.
A sequence diagram generally shows the interaction between objects in a sequential order. It is for users to document and understand requirements in a new system. In software development, this type of diagram is used to represent the architecture of a system.
Communication Diagram (Collaboration Diagram)
A Communication diagram is used to display sequenced communications between objects with the focus on primary objects and their relationships. Communication diagrams usually use number schemes and pointing arrows to show message flow. Moreover, compared with sequence diagrams, communication diagrams are much easier to be designed, but contains fewer details when drafting documentation for systems.
A Timing diagram is a special form of the Sequence diagram that is used to show the behavior of objects over a certain time constraint. It is similar to the form of, for example, the history of iPhone development, or the growing trend of an international enterprise.
Interaction Overview Diagram
An Interaction Overview diagram displays a sequence of behaviors and helps users simplify complex interactions (rectangular frames) into simpler forms in a system. It can be considered as a mixture of specialized activity and sequence diagrams, but Interaction Overview diagrams have more elements than Activity diagrams such as interaction, time constraint and more.
More Free UML Diagram Templates
Here are more templates of UML diagrams for you to easily understand all of these UML sub-categories. All of these are editable with the free download UML diagram software. Feel free to click on any of them to see more details.
|Student Management Use Case Diagram||UML Sequence Diagram Template||Bank System Use Case Template|
|UML Component Diagram Template||Ticket UML Collaboration Template||Deployment Chart Template|
UML Diagram Symbols
There are many UML diagram symbols in each of the UML categories. Among all of these symbols, the Class diagrams symbols (defining attributes and operations of classes), the Activity diagram symbols (used to show states and activities) and the Use case diagram symbols (shown with different types of arrows) are the most popular ones.
How to Create a UML Diagram Easily?
Simply follow these steps to quickly create a professional-looking UML diagram.
1. Open a preset UML diagram template or a blank drawing page for your work. Double-click one of the icons in the UML Model Diagram category to start creating.
2. Drag and drop UML standard shapes from the built-in libraries. Adjust the shape size to fit the drawing board.
3. Align or group UML shapes for the appropriate locations.
4. Connect UML shapes by adding more connection points on the shapes or by using the preset relationship lines.
5. Double-click to edit default shape text.
6. Further format your UML diagram by changing the colors of shapes/lines, trying different diagram theme and adding background etc.
7. Print, save to built-in personal/team cloud, or export to different formats including Visio, MS Office, PDF and more.
Create Your Own UML Diagrams Right Now!
Simply use Edraw Max for efficient UML diagramming. Enjoy Edraw's polished drawing board, extensive UML shapes built-in library, quick-exporting options for a wide range of formats including Visio, preset team and personal cloud account for your communications and the convenient drag-and-drop editor. Explore more features by clicking on the free download button at the end of this page.