What Is a Composite Structure Diagram and How to Make One

A step-by-step guide on creating and mastering UML composite structure diagrams.

uml composite structure diagram tutorial

Unified Modeling Language is very important in software engineering. It makes it easier to design system setups and operations. In UML, there are many diagram types. It's essential to always analyze Composite Structure Diagrams. They show how sub-elements become one working component.

In system design, the Composite Structure Diagrams are route maps. They help show dependencies and interactions between objects/ports. They describe the relationships and dependencies. They also cover the organization and functionality of the software systems. These systems support the development of sound architectural models. These models can scale and enforce high availability standards.

Readers will understand how to design Composite Structure Diagrams. They show how components relate as a system. Further, they will learn how to understand such figures. They show if a system is efficient and correct. This understanding helps in making the right decision on system architecture.

In this article
  1. What Is a Composite Structure Diagram?
  2. Purpose of Composite Structure Diagram
  3. Components of a Composite Structure Diagram
  4. How to Draw a Composite Structure Diagram
  5. Deriving Composite Structure Diagram from Class Diagram
  6. Conclusion

Part I. What Is a Composite Structure Diagram?

A Structure Diagram is a graphical model in the Unified Modeling Language. It shows the inner structure of a system. This helps in how the different parts of the system are configured, interfaced, and coordinated to help execute the system assignments.

A UML composite structure diagram has components, ports, connectors, and connections. Components refer to the various structures in the system which may include the classes, objects, or sub-systems. Ports act as mediator entities that interact between the components; they both transmit and receive signals. Communication pathways are likewise defined by connectors denoting data or control flow between connected modules.

Components, hierarchies, and associations show how components are arranged within the system. They use relationship types like aggregation or composition. The diagram shows the details and complexities of the parts and how they connect. This makes it useful for making and using the system. It's especially helpful in design and maintenance.

Part II. Purpose of Composite Structure Diagram

UML Composite Structure Diagrams are quite useful.

They support, among other things, the modeling and comprehension of complex system designs. It helps architects and developers understand the structure and interaction of a system's parts. It shows how the parts work to support specific functions.

Also, like the life cycle, these diagrams help communication between key participants. They do this with an effective show of the systems inside. They plan and implement the system. They also decide how to organize its parts, the paths of communication, and the scale of its capabilities, among other things.

Composite Structure Diagrams play a vital role in software engineering by aiding in system modeling, fostering understanding of system structures and interactions, and facilitating communication among project stakeholders. Their utilization contributes to the creation of well-designed and robust software systems that meet the needs of users and stakeholders effectively.

Part III. Components of a Composite Structure Diagram

The UML has a key feature. It makes a Composite Structure Diagram. It has several main parts representing a system's structure and interactions. It also includes four sub-classes namely structured classifiers, parts, ports, connectors, and collaborations.

Structured Classifier:

It is the basic component of a composite structure diagram, called the building block. They mirror the contained parts, strong and weak ports, and connectors specify the internal structure of a class or part. This feature makes it easy to see the inside and behavior of a system component. It also shows the interactions of its sub-components. An example of such a structured classifier is a class, component, node, or collaboration.

structure classifier


A composite structure diagram shows how parts are in a structure. Parts are the roles of instances of classes in a containing classifier. Rectangles in the diagram represent roles and types of parts. The text inside a rectangle describes the part. They may also contain multiplicities, values that define how many instances should be able to take that role.



These are mainly entry and exit points that interface a structured classifier with the external world or other interfaces. This makes them define the contact points where interactions take place. They are specifically at the boundary and interact with other systems within the system. Ports are small squares. They are located near the boundary of the classifier. They are labeled with an interface or a protocol designation.



They show the relationships between some parts. Also, they show the relationships between parts and ports in the given classifier. They describe how the instances interact or cooperate and may define associations, relations, or connection paths. Connectors are produced as lines between parts or ports and can be labeled depending on the connection type.



In a composite structure diagram, they show how prototype classes are structured. They also show the roles that these classes take when they interact or behave. Collaboration shows how objects can be combined to do a task or action. They are drawn with dashed lines. They contain annotations describing the roles. The application includes interaction diagrams showing roles in a certain case.


Part IV. How to Draw a Composite Structure Diagram

Step 1: Identify the Structured Classifiers

Decide the distinct structure classifiers (for example, classes, components, nodes) in your system. To draw it, Use the large rectangle to represent each structured classifier in your diagram.

Step 2: Define the Parts

Name the components present inside each structured classifier concerning their roles and types. These parts should be visualized as smaller rectangles nested within the structured classifier and should be named according to the role and type they perform. Indicate multiplicities if applicable.

Step 3: Add Ports to the Structured Classifiers

From the above structure, we can only identify ports for each classifier. Place small squares on this boundary to signify the ports of the structured classifiers. Label each port with the appropriate interface or protocol, indicating whether it is required or provided.

Step 4: Connect Parts and Ports with Connectors

The use of the connectors is to represent the links between parts or between parts and ports. Draw lines connecting the parts or ports, labeling them if necessary to describe their nature or constraints. Ensure connectors clearly show the communication pathways within the structured classifier.

Step 5: Represent Collaborations

Explain this in your system. Show how structured classifiers and their sub-classifiers interact to create behaviors. Use dashed line symbols for cooperation, and sign it to describe the parts. If there are particular conversations or modes, one might include the interaction diagrams.

Part V. Deriving Composite Structure Diagram from Class Diagram

Let's model the online dealership of cars using a class diagram.

We have a class for delivery which may be aggregated by the car class, which itself is composed by the dealership class.

class diagram

Everything looks like it ends up inside the dealership, so we can create a composite structure diagram to see what it's made of.

composite structure diagram uml

To make a Composite Structure Diagram from a Class Diagram, you must follow a detailed process. It involves turning the static design of a system into a model. The model shows the internal static structure of Classes/objects that are inherent in a certain class.

The process starts by reviewing the Class Diagram. The goal is to decide on the classes and how they relate. Relationships that happen within those classes are specified by attributes or references where they act as composites that are a part of the composites structure.

Then connectors are used to show how these elements are affiliated in the class; such as composition/aggregate relationships. These parts may be given key names or adjectives to indicate their role or location within this class.

Lastly, based on the main class's purpose and functionality, we make the composite structure diagram. The main class and its parts form the diagram. Connectors show how the parts work.


UML is a proven way to visually describe systems. Among the graphical patterns used in it, one is a composite structure diagram. Composite Structure Diagrams are important in the development language. They offer a schematic view of systems. This helps the developer see complex systems better. Such systems are hard to understand and work on.

These diagrams show the internal architecture's details and how its components are related. They are especially useful for showing architecture during development. Composite Structure Diagrams are indispensable instruments for designing robust, and adaptable software applications. Their ability to provide a detailed overview of system architectures makes them essential for ensuring the success of software projects.

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Zac Jenkins
Zac Jenkins Jul 04, 24
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