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Aggregation vs. Composition: What's the Difference?

Edited by Huma Saeed || By Sumera Saeed || Published on February 3, 2024
Aggregation is a weak association where entities can exist independently, while composition is a strong association where the life cycle of the contained entity depends on the container.

Key Differences

Aggregation refers to a relationship where the child can exist independently of the parent. For example, a team and a player; a player can exist without a team. Composition, on the other hand, implies a relationship where the child cannot exist without the parent. For example, a house and a room; a room doesn't typically exist without a house.
Sumera Saeed
Feb 03, 2024
In aggregation, the entities have their own lifecycle and ownership. This means that destruction of the parent entity does not necessarily destroy the child entities. In composition, the child entity's lifecycle is tightly coupled with the parent's lifecycle. The destruction of the parent entity leads to the destruction of the child entities.
Huma Saeed
Feb 03, 2024
Aggregation represents a “has-a” relationship with less dependency, where association is more loosely coupled. For instance, a university and its departments can be seen as an aggregation; departments can theoretically exist independently. Composition, however, is more rigidly coupled, representing a part-of relationship. For example, a car and its engine; the engine is an integral part of the car.
Sumera Saeed
Feb 03, 2024
Considering ownership, in aggregation, the child can be associated with multiple parent entities. A book can belong to multiple libraries (aggregation). In composition, the child entity is owned by a single parent entity. A heart is part of a specific body (composition).
Janet White
Feb 03, 2024
In terms of lifetime, aggregation allows for the independent existence of entities. A class and its students; students will continue to exist even if the class is dissolved. Composition denotes a scenario where if the parent entity ceases to exist, its child entities also cease to exist. A company and its departments; if the company shuts down, the departments also cease to exist.
Sumera Saeed
Feb 03, 2024
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Comparison Chart

Dependency

Entities can exist independently.
Child entity's existence is dependent on the parent.
Sumera Saeed
Feb 03, 2024

Lifecycle

Separate lifecycles for parent and child entities.
Child's lifecycle is tied to the parent's lifecycle.
Sumera Saeed
Feb 03, 2024

Ownership

Child can be associated with multiple parents.
Child is owned by a single parent.
Sumera Saeed
Feb 03, 2024

Relationship Type

“Has-a” relationship, loosely coupled.
“Part-of” relationship, tightly coupled.
Sumera Saeed
Feb 03, 2024

Existence

Child entities can exist independently of the parent.
Child entities do not exist independently of the parent.
Harlon Moss
Feb 03, 2024
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Aggregation and Composition Definitions

Aggregation

It refers to a group or mass of distinct or varied things, people, or elements.
An aggregation of diverse cultures enriches the community.
Huma Saeed
Jan 23, 2024

Composition

Composition is the act or process of combining parts or elements to form a whole.
The composition of the committee was carefully chosen to reflect diverse opinions.
Sumera Saeed
Jan 23, 2024

Aggregation

In business, it's the gathering of individuals or companies into a group.
The aggregation of small firms created a more formidable market presence.
Janet White
Jan 23, 2024

Composition

In chemistry, it's the nature and proportion of elements in a substance.
The chemical composition of water is two hydrogen atoms bonded to one oxygen atom.
Aimie Carlson
Jan 23, 2024

Aggregation

Aggregation is a collection or assembly of items.
The aggregation of data from different sources ensured a comprehensive analysis.
Sumera Saeed
Jan 23, 2024

Composition

It refers to the arrangement or structure of elements in a work of art or literature.
The novel’s composition was praised for its unique narrative structure.
Sumera Saeed
Jan 23, 2024

Aggregation

In biology, it's the clustering of organisms in a population.
The aggregation of bees around the hive is a defensive mechanism.
Aimie Carlson
Jan 23, 2024

Composition

In music, it's the creation of a musical work.
Mozart's compositions are renowned for their complexity and beauty.
Sumera Saeed
Jan 23, 2024

Aggregation

In computing, it's the process of combining multiple data entities into a single one.
Aggregation of multiple datasets is common in statistical analysis.
Aimie Carlson
Jan 23, 2024

Composition

In photography and visual arts, it's the arrangement of visual elements in a work.
The composition of the photograph highlighted the contrast between light and shadow.
Harlon Moss
Jan 23, 2024

Aggregation

Constituting or amounting to a whole; total
Aggregate sales in that market.
Sumera Saeed
Jan 22, 2024

Composition

The combining of distinct parts or elements to form a whole.
Sumera Saeed
Jan 22, 2024

FAQs

What is composition?

Composition refers to a relationship where one entity is composed of, or dependent on, the other.
Huma Saeed
Feb 03, 2024

Is a composition entity independent of its parent?

No, in composition, the child entity is dependent on the parent and cannot exist independently.
Harlon Moss
Feb 03, 2024

What is aggregation?

Aggregation is a concept where a relationship between two entities is established such that one represents a collection of the other.
Sumera Saeed
Feb 03, 2024

Can an aggregation exist without its parent entity?

Yes, in aggregation, the child entity can exist independently of the parent.
Sumera Saeed
Feb 03, 2024

How does aggregation affect the lifecycle of an entity?

In aggregation, the lifecycle of entities is not mutually dependent.
Sumera Saeed
Feb 03, 2024

How does composition affect the lifecycle of an entity?

In composition, the destruction of the parent often means the destruction of the child entities.
Sumera Saeed
Feb 03, 2024

Can a child entity in composition belong to multiple parents?

No, in composition, a child entity is typically associated with a single parent.
Harlon Moss
Feb 03, 2024

Is composition a strong or weak association?

Composition is a strong association, indicating a higher degree of dependency.
Janet White
Feb 03, 2024

What is an example of aggregation?

A library and books; books can exist outside of the library.
Sumera Saeed
Feb 03, 2024

Can an entity be part of multiple aggregations?

Yes, an entity can be part of multiple aggregations.
Aimie Carlson
Feb 03, 2024

What is an example of composition?

A house and rooms; rooms are integral parts of a house.
Sumera Saeed
Feb 03, 2024

What kind of relationship does aggregation imply?

Aggregation implies a “has-a” relationship.
Sumera Saeed
Feb 03, 2024

Are composition relationships easily altered?

No, composition relationships are not easily altered due to the dependency of the entities.
Sumera Saeed
Feb 03, 2024

Is aggregation commonly used in database relationships?

Yes, aggregation is commonly used in databases to define relationships between tables.
Janet White
Feb 03, 2024

Can aggregation relationships be easily broken?

Yes, relationships in aggregation can be more easily altered or broken.
Aimie Carlson
Feb 03, 2024

What kind of relationship does composition imply?

Composition implies a “part-of” relationship.
Aimie Carlson
Feb 03, 2024

Does aggregation allow shared ownership?

Yes, in aggregation, entities can have shared ownership.
Harlon Moss
Feb 03, 2024

Does composition allow shared ownership?

No, in composition, the parent entity has exclusive ownership of the child entities.
Sumera Saeed
Feb 03, 2024

Is composition relevant in software development?

Yes, composition is highly relevant in software development, particularly in object-oriented programming.
Aimie Carlson
Feb 03, 2024

Is aggregation a strong or weak association?

Aggregation is considered a weaker association compared to composition.
Aimie Carlson
Feb 03, 2024
About Author
Written by
Sumera Saeed
Sumera is an experienced content writer and editor with a niche in comparative analysis. At Diffeence Wiki, she crafts clear and unbiased comparisons to guide readers in making informed decisions. With a dedication to thorough research and quality, Sumera's work stands out in the digital realm. Off the clock, she enjoys reading and exploring diverse cultures.
Edited by
Huma Saeed
Huma is a renowned researcher acclaimed for her innovative work in Difference Wiki. Her dedication has led to key breakthroughs, establishing her prominence in academia. Her contributions continually inspire and guide her field.

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