What is a Component Diagram in UML?
Component diagrams are integral to building your software system. They help your team understand the structure of existing systems and then build new ones.
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What is a Component Diagram in UML?
In UML, a component diagram visually represents how the components of a software system relate to one another. To build one, try using Lucidchart’s custom component diagram shape library. Component diagrams should communicate:
- The scope of your system.
- The overall structure of your software system.
- Goals that it helps human or non-human entities (known as actors) achieve.
Employing Component Diagrams
A component diagram in UML gives a bird’s-eye view of your software system. Understanding the exact service behavior that each piece of your software provides will make you a better developer. Component diagrams can describe software systems that are implemented in any programming language or style.
UML is a set of conventions for object-oriented diagrams that has a wide variety of applications. In component diagrams, the Unified Modeling Language dictates that components and packages are wired together with lines representing assembly connectors and delegation connectors. To learn more about UML and its uses, check out this guide to “What Is UML?”
Why Make a Component Diagram?
Though component diagrams may seem complex at first glance, they can be invaluable in building your system. Component diagrams can help your team:
- Imagine the system’s physical structure.
- Pay attention to the system’s components and how they relate.
- Emphasize the service behavior as it relates to the interface.
Building Blocks of Component Diagrams
Component diagrams range from simple and high-level to detailed and complex. Either way, you'll want to familiarize yourself with the appropriate UML symbols. These are some shape types you will commonly encounter when reading and building component diagrams:
- Component - an entity required to execute a stereotype function. A component provides and consumes behavior through interfaces, as well as via other components. Think of components as a type of class. In UML 1.0, a component is modeled as a rectangular block with two smaller rectangles protruding from the side. In UML 2.0, a component is modeled as a rectangular block with a small image of the old component diagram shape.
- Node - nodes are hardware or software objects, which are of a higher level than components. Boxes represent nodes in Lucidchart.
- Interface - show input or materials that a component either receives or provides. Interfaces can be represented with textual notes or symbols—such as the the lollipop, socket, and ball-and-socket shapes.
- Port - symbolized with a small square, ports specify a separate interaction point between the component and the environment.
- Package - groups together multiple elements of the system. Packages are represented by file folders in Lucidchart. Just as file folders group together multiple sheets, packages can be drawn around several components.
- Note - this allows a developer to affix a meta-analysis to the component diagram. Notes look like sticky notes in Lucidchart.
- Dependency - shows that one part of your system depends on another. Dependencies are represented by dashed lines linking one component (or element) to another.