Model Aggregation Composition Associations - Exercise Result

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Exercise solution — This graphic depicts a UML (Unified Modeling Language) class diagram illustrating the relationships between various entities in a car configuration system. Here is a detailed breakdown:

**Car and CarConfiguration**:

A `Car` entity is linked to a `CarConfiguration` entity by a 0..* (zero to many) relationship, indicating that a car can have multiple configurations over time.

**Driver and ConfigurationAssessment**:

The `Driver` entity is associated with `ConfigurationAssessment` via the relationship "is tested by". This is a 0..* relationship, meaning multiple drivers can test multiple configuration assessments.

**CarConfiguration and its Parts**:

`CarConfiguration` includes a **Transmission** and an **Engine**:

Both `Transmission` and `Engine` are associated with `CarConfiguration` using an aggregation relationship (indicated by a hollow diamond). This signifies that the transmission and engine are parts of the car configuration but can exist independently of it.

**Engine Composition**:

The `Engine` is composed of:

**Carburetor** (1 relationship): Each engine has exactly one carburetor.

**Pistons** (8 relationship): Each engine is composed of eight pistons.

**Plugs** (8 relationship): Each engine also includes eight plugs.

These are shown with a composition relationship (indicated by a filled diamond), meaning the carburetor, pistons, and plugs are integral parts of the engine and cannot exist independently of it.

**Key UML Symbols Used:**

**Aggregation (hollow diamond)**: Indicates a "whole-part" relationship where the parts can exist independently of the whole.

**Composition (filled diamond)**: Indicates a "whole-part" relationship where the parts cannot exist independently of the whole.

**Multiplicity**: Numbers (e.g., 0..*, 1, 8) show how many instances of a class can be associated with another class.

**Summary of Relationships:**

`CarConfiguration` is tested by `Driver` via `ConfigurationAssessment`.

`CarConfiguration` aggregates `Transmission` and `Engine`.

`Engine` is composed of `Carburetor`, `Pistons`, and `Plugs`.

Each car can be configured with different engine and transmission combinations. The configuration is composed of (aggregation) an engine and a transmission. Each driver tests each car configuration. The association class ConfigurationAssessment contains the details of the drivers' evaluations. The engine is composed of the carburetor, pistons, and plugs (along with other unnamed parts).
However, these parts become permanent parts of the engine once installed, so we use composition instead of aggregation.