Package diagram tutorial

5 min

Use this guide to learn everything you need to know about package diagrams, including what benefits they provide, how to properly build them, and more. With our UML diagram tool, you can take advantage of the structure and organization provided by package diagrams to simplify even the most complicated of UML classifiers.

What is a package diagram?

Package diagrams are structural diagrams used to show the organization and arrangement of various model elements in the form of packages. A package is a grouping of related UML elements, such as diagrams, documents, classes, or even other packages. Each element is nested within the package, which is depicted as a file folder within the diagram, then arranged hierarchically within the diagram. Package diagrams are most commonly used to provide a visual organization of the layered architecture within any UML classifier, such as a software system.

Benefits of a package diagram

A well-designed package diagram provides numerous benefits to those looking to create a visualization of their UML system or project.

They provide a clear view of the hierarchical structure of the various UML elements within a given system.
These diagrams can simplify complex class diagrams into well-ordered visuals.
They offer valuable high-level visibility into large-scale projects and systems.
Package diagrams can be used to visually clarify a wide variety of projects and systems.
These visuals can be easily updated assystems and projects evolve.

Basic components of a package diagram

The makeup of a package diagram is relatively simple. Each diagram includes only two symbols:

Symbol	Name	Description
	Package	Groups common elements based on data, behavior, or user interaction
	Dependency	Depicts the relationship between one element (package, named element, etc) and another

These symbols can be used in a variety of ways to represent different iterations of packages, dependencies, and other elements within a system. Here are the basic components you’ll find within a package diagram:

Package

A namespace used to group together logically related elements within a system. Each element contained within the package should be a packageable element and have a unique name.

Packageable element

A named element, possibly owned directly by a package. These can include events, components, use cases, and packages themselves. Packageable elements can also be rendered as a rectangle within a package, labeled with the appropriate name.

Dependencies

A visual representation of how one element (or set of elements) depends on or influences another. Dependencies are divided into two groups: access and import dependencies. (See next section for more info.)

Element import

A directed relationship between an importing namespace and an imported packageable element. This is used to import select individual elements without resorting to a package import and without making it public within the namespace.

Package import

A directed relationship between and importing namespace and an imported package. This type of directed relationship adds the names of the members of the imported package to its own namespace

Package merge

A directed relationship in which the contents of one package are extended by the contents of another. Essentially, the content of two packages are combined to produce a new package.

Dependency notations in a package diagram

Package diagrams are used, in part, to depict import and access dependencies between packages, classes, components, and other named elements within your system. Each dependency is rendered as a connecting line with an arrow representing the type of relationship between the two or more elements.

There are two main types of dependencies:

Access: Indicates that one package requires assistance from the functions of another package.
Example:

Import: Indicates that functionality has been imported from one package to another.
Example:

Dependencies can also be broken down further into the following categories:

Usage

Occurs when a given named element requires another for its full definition and deployment. Example: client and supplier.

Abstraction

Relates two elements representing the same concept at different levels of abstraction within the system (usually a relationship between client and supplier).

Deployment

Depicts the deployment of an artifact to a deployment target.

Package diagram example

Take a look at the following template to see how a package diagram models the packages within a basic e-commerce web app. Click on the template to modify it and explore how you can show the structure of any designed system at a package level.

Using packages with other UML diagrams

As we’ve shown earlier in this guide, packages are UML constructs that can be used to organize the elements within any UML classifier in a variety of UML diagrams. Package diagrams are most commonly found used in:

Use-case diagrams: Each use-case is depicted as an individual package
Class diagrams: Classes are organized into into packages

Packages can also be used within other UML model types to organize and arrange elements such as classes, data entities, and use cases. By fuzing the package diagram structure with other UML diagrams, you can simplify any model type, making it easier to understand.

Model diagrams

Package diagrams can also be used in conjunction with model diagrams—a type of UML auxiliary structure diagram used to depict the logical, behavioral, or structural aspects of a system. Even simple models can be difficult to understand without some type of visual organization. The use of packages can provide users with a high-level view of a model with unambiguous named references for each of the elements it contains. In addition, clearly labeled dependencies can clarify the relationships between each element.

Everything you need to make a diagram

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Frequently asked questions

What is a package diagram?

Package diagrams are structural diagrams used to show the organization and arrangement of various model elements in the form of packages, where each package groups related UML elements like diagrams, documents, classes, or other packages in a hierarchical structure.

What are the main components of a UML package diagram?

Package diagrams include only two symbols: packages (depicted as file folders that group common elements) and dependencies (connecting lines with arrows that show relationships between elements).

What are the benefits of using a package diagram?

Package diagrams provide a clear view of hierarchical structure, simplify complex class diagrams, offer high-level visibility into large-scale projects, and can be easily updated as systems evolve.

What is the difference between access and import dependencies?

Access dependencies indicate that one package requires assistance from the functions of another package, while import dependencies show that functionality has been imported from one package to another.

What is a packageable element?

A packageable element is a named element that can be owned directly by a package, including events, components, use cases, and packages themselves, each with a unique name.

What is the difference between package import and package merge?

Package import is a directed relationship that adds the names of members from an imported package to the importing namespace, while package merge combines the contents of two packages to produce a new package.

How are package diagrams used with other UML diagrams?

Package diagrams are commonly used with use case diagrams (where each use case is depicted as a package) and class diagrams (where classes are organized into packages) to simplify and organize model elements.

Can package diagrams show nested structures?

Yes, each element is nested within packages depicted as file folders and arranged hierarchically within the diagram, with packages able to contain other packages.

Everything you need to make a UML diagram

In addition to our online UML diagram tool, Lucidchart offers support and training resources to help you branch out to any type of diagram.

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Contents

Package diagram tutorial

What is a package diagram?

Benefits of a package diagram