The Unified Modeling Language (UML) is a comprehensive modeling language for software development. It allows developers to create models of systems that are visual in nature. Many software development methodologies use UML diagrams in their process to develop software.
In order to make the best use of UML diagrams, it is important to know which free UML diagram tool will be most appropriate for your needs.
What is a class diagram used for?
Class diagrams are used in software engineering to describe the structure of a system. A class diagram uses Unified Modeling Language (UML) to show the classes, attributes, methods (or operations), and their relationships to each other, in the system. Essential to object-oriented modeling, a class diagram can be used to model the data structure or to design the system in detail.
In a class diagram, a class is any group of objects in the system that share similar roles. These classes have relationships to each other. The class can be considered a blueprint for objects, as they are used to define objects in the system and determine what they can do and how they are created.
For a developer, a class diagram provides the opportunity to sketch out the static view of an application or system before any coding begins. This can be vital for communicating requirements to stakeholders and for optimizing development or even maintenance at later stages in the project.
The basic elements used to create a class diagram are the class name, attributes, and methods (or operations). Classes are usually represented by a rectangle with three distinct sections separated by horizontal lines.
Class name
Each class is represented by a rectangle in the diagram, with the name of the class in the top part. Class names are usually centered, written in bold, and start with a capital letter.
Attributes
Attributes are data elements that are contained in every object of a class and have a value for each of these objects. Attributes are shown in the middle of the class rectangle, are aligned left, and the first letter is lowercase (note that it is very common to use camelCase for both attributes and methods).
Methods (operations)
Classes have particular operations for dealing with communication with other classes. Methods are shown in the bottom part of the class rectangle and, like attributes, are aligned left with the first letter in lowercase.
- The visibility of both attributes and methods can be specified by means of symbols before the name. + means public, – means private, # means protected, ~means package.
- If an attribute or method is derived from other values in the system, this can be indicated with a / before the name.
- Both attributes and methods can also have extra parameters, such as type, initial values, and constraints.
Gleek enables you to create a class with its attributes and methods with just a few lines of the unique Gleek syntax.
Relationships
The connections between classes are called relationships. There are several different types, each shown with its own connecting line, either with or without an arrow at the end.
Association
Association indicates a static relationship between two classes. Association relationships will usually include text to explain the nature of the relationship.
Aggregation
Aggregation shows that one or more classes are part of another class, or are contained by it. However, if all the contained classes are removed, the container will persist.
Composition
Composition is a stronger relationship than aggregation. It indicates that the classes contained depend upon the existence of the container. If the container class is removed, they cannot persist.
Dependency
Dependency indicates that one class depends on another, in that a change in one class may result in changes in the other.
Multiplicity
Multiplicity is an association relationship and indicates that at least one of the two classes refers to the other when creating instances of itself. In other words, it shows the cardinality of the relationship.
Generalization/inheritance
When a particular class is considered to be a child of another class, it will inherit the same functionalities of the parent class. The specific class provides additional properties to the parent class, but is still compatible with it.
Realization/implementation
This indicates that a particular class is responsible for the implementation of some of the functionality of another class. The relationship defines this functionality for the class that is implementing, or realizing, it.
1) Edraw Max
Edraw Max is a UML builder software that helps you to make diagrams using ready-made symbols and templates. It allows you to import your drawings to file formats such as PDF, PPT, Word, HTML, etc.
Features:
- You can create a flowchart, mind map, UML, electrical diagrams, network diagrams, etc.
- It provides a user-friendly interface similar to MS Word.
- Edraw Max helps you to share designs anytime, anywhere.
- This tool provides 280+ latest flowchart and diagram solutions.
2) Moqups
Moqups is online tool that enables you to make flowchart, and UML diagrams with minimal effort. It allows you to drag and drop shapes to visualize any flow.
Features:
- You can collaborate easily with other people.
- Export diagram to PDF or PNG.
- Easy to share your project link with stakeholders.
- Includes numerous shapes and drawing arrows.
- You can resize, rotate, and move shapes.
- Offers readymade customizable templates.
- Guru99 users get 20% off with coupon “GURU20”
3) Visio
Microsoft Visio is a popular chart and visualization software. It belongs to office family so it can easily be integrated with other Microsoft office products.
Features:
- Visio helps you to create professional diagram by creating flowcharts, diagrams, org charts, engineering designs, and more.
- Allows you to connect flowcharts and diagrams to real-time data.
- It allows you to work together on diagrams from a web browser, from almost anywhere.
4) ConceptDraw
ConceptDraw DIAGRAM offers a complete range of business graphic documentation solutions. These UML solutions offer business-specific add-ons which offer an extensive variety of workflow requirements.
Features:
- ConceptDraw DIAGRAM v12 offers powerful and comprehensive drawing tools.
- Helps you to empower your communication processes and improve your presentation techniques.
- The tool is an ideal suite for building plan software.
- You can use very important business metrics and track with live object technology.
5) StarUML
StarUML is a UML diagram modeling tool. It is one of the best UML software that provides eleven types of diagram. StartUML 2 is compatible with UML 2.x versions.
Features:
- Allows you to create Obje3ct, Use case, Deployment, Seque3nce, Communication, Activity, and profile Diagram.
- This UML diagram software allows you to discover and install third-party extensions.
- Work with same UX in multiple platforms including macOS, Windows, and Linux.
- No limit for using this commercial software for evaluation.
6) Umbrello
Umbrello is a UML modeling tool. It runs under KDE and Linux. It is one of the best UML diagram tool which supports code generation as well as reverse engineering for C++ and Java.
Features:
- It allows you to create diagrams of software and another system in a standard format
- It helps you to check the screenshot to see umbrello in action.
- Offers handbook to give instruction to Umbrello and UML modeling.
7) UML Designer Tool
UML Designer tool offers a set of common diagrams to work with UML 2.5 models. The tool provides an easy method for the transition from UML to domain-specific modeling.
Features:
- Allows user to re-use provided representations and work in total transparency on both DSL and UML models
- This UML software helps you to create a Class diagram, Component Diagram, and composite structure Diagram
- This UML diagram software allows you to use legacy UML models and start working with DSL.
8) Altova
Altova UModel is another useful UML tool which makes visual software design practical for any project. Visually design application models in UML which can be generated using Java, C++, C#, or Visual Basic.
Features:
- Intuitive Visual Modeling for all UML Diagrams
- Helper windows allow you to build your desired models.
- It allows you to add hyperlinks to any element in any UML diagram.
- You can assign an element to the specific layer, and layers can be locked to prevent changes.
9) Umple
Umple is an open source model for integrating textual UML constructs in programming languages, code generation or using simple UML modeling method.
Features:
- It allows developers to embed modeling concepts patterns, generation templates, and other abstractions in traditional code.
- Umple tool helps users to learn UML faster.
- The tool can works online, as Eclipse plugin, and also stand-alone command-line Jar.
10) Visual Paradigm
Visual Paradigm is a software design tool which is tailored for engine software projects. This UML editor tool helps the software development team to a model business information system and development processes.
Features:
- It offers support for BPMN, UML, ERD, DFD, SysML.
- It offers a complete tool like for process analysis, system design, database design, etc.
- Offers user story feature to capture and maintain user’s needs.
11) WhiteStarUML
WhiteStarUML is another important Universal modeling tool which offers all the feature which can be adapted to the modern environment like the support of Unicode strings.
Features:
- Windows 7, 8, 10 versions supported.
- This UML diagram maker provides the best functionality expected from a UML tool like a large selection of supported diagrams.
- Good usability giving the overall look and feel of a serious programming environment.
12) Draw.IO
Draw.IO is a free online UML tool. It is one of the best UML tools that allows users to create and manage the drawing easily these tools. A lot of the wide and early share available with this tool.
Features:
- No limit on the number of sizes
- Templates are present in software design itself.
- This free UML diagram tool allows you to save the model in your preferred location
13) GenMyModel
GenMyModel began as a UML tool but, today It is expanded to cover also business modeling with Archimate and BPMN support. It offers a centralized model repository which allows easy and simultaneously models collaboration.
Features:
- Share your knowledge with versioning and access right management.
- Useful for presentations to management and project stakeholders.
- Helps you to combines the power of desktop modeling tools with a modern web solution.
- Allows you to directly import or export as PDF documents.
14) UMLetino
It is accessible to the user as an open source UML diagram tool for developing UML diagrams. It can directly run in your browser, and it does not need any installations.
Features:
- Diagrams can be exported as XML or any other image files.
- Allows you to store diagrams with other teammates
- It is one of the best open source UML tools that offers you to export diagrams in SVG, Gif or JPEG format.
15) Diagramo
Diagramo is a free and open source HTML5 online flowchart software. It is easy to download and install on your server.
Features:
- This UML diagram software allows you to save diagrams as images
- It is flow chart focused software which only one kind of UML diagrams.
16) Astah
Astah is a UML editor which is integrated with Mind mapping features. It is one of the best UML tool that helps you to visualize the essence of your ideas before you code.
Features:
- Faster to create UML compares with Excel or non-UML-specific drawing tools.
- Visualize requirements and functional requirements, all the relations between them and to other model elements.
- Merge, exclusive control, copy & paste support.
17) Visual Modeling Software
Microfocus is a visual modeling tool which allows business and software development to analyze and design software architecture.
Features:
- This platform offers you to model enterprise architectures in such a way that requirements, architectures, and code are always in sync
- Offers Model-driven Architecture and data modeling systems
- Livesource technology feature allows you to use programming language source code to management elements and eliminate unnecessary work
18) BOUML
BOUML is a free UML2 tool which includes modeler. This helps you to specify and generate code in C++, Java, Php, Python, and MySQL.
Features:
- It runs under Windows, Linux and MacOS X versions.
- it helps you to program simultaneously in C++, Java, Php, Python, MySQL, etc.
- it is very fast and not need much memory to manage several thousands of classes, see benchmark
19) Dia
Dia is a full-featured diagramming program which is licensed under GPL. It allows you to draw various types of diagrams and has special objects to help you to draw ER diagrams, UML diagrams, flowcharts, network diagrams, and many other diagrams.
- It offers support for new shapes by writing simple XML files, using a subset of SVG to draw the shape.
- It allows you to export diagrams to a number of formats, including EPS, SVG, XFIG, WMF, and PNG.
Conclusion
CClass diagrams are part of the UML diagram set. Like all other diagrams, they are used to model information about software or hardware systems. A class diagram is described as a pictorial representation of either the system under development or its environment.