Question

In the context of object-oriented programming, what parts of an object are used to store declarative knowledge? What parts are used to store procedural knowledge?

Short answer

Objects store declarative knowledge in data fields and procedural knowledge in methods.

Step-by-step solution

Understanding Declarative Knowledge

Declarative knowledge refers to information stored within an object that defines its attributes or state. In object-oriented programming, this type of knowledge is stored in the object's data fields, also known as properties or instance variables. These fields hold values that represent the characteristics of the object.

Identifying Procedural Knowledge

Procedural knowledge involves the actions or behaviors an object can perform. In object-oriented programming, this is encapsulated in methods or functions associated with the object. These methods define how an object behaves or interacts with other objects, thereby implementing procedural knowledge.

Distinguishing Between Both

To effectively distinguish between declarative and procedural knowledge in an object-oriented context, remember that declarative knowledge is static information (data fields), while procedural knowledge is dynamic behavior (methods). Recognizing this distinction helps in understanding how objects operate and interact in a program.

Key concepts

Declarative Knowledge

In object-oriented programming, declarative knowledge represents the fixed attributes or characteristics of an object. It focuses on **what** an object is or has, rather than **what it does**. In a class, this type of knowledge is typically stored in data fields, often referred to as properties or instance variables.

For instance, consider a `Car` object. Its declarative knowledge might include:

• Color
• Make
• Model
• Year

These are the data fields that hold specific details about the car, such as it being red or manufactured in 2020.

To encapsulate declarative knowledge effectively, it's important to choose meaningful and descriptive names for data fields. This clarity aids in maintaining code readability and understanding across the program.

Procedural Knowledge

Procedural knowledge in object-oriented programming refers to the capabilities or actions associated with an object. It is concerned with the **how** an object behaves or functions. This type of knowledge is encapsulated within methods or functions.

Taking the `Car` object example further, its procedural knowledge consists of actions such as:

• Start engine
• Drive
• Turn
• Honk

Each of these actions is represented through methods in the class that define how the object interacts with the world. For example, a `startEngine()` method may involve a sequence of steps such as engaging the ignition system.

Well-defined methods not only make the class functional but also modular and reusable. Every method should have a single responsibility to make it easy to understand and maintain.

Data Fields

Data fields, also known as instance variables or properties, are where an object stores its declarative knowledge. These fields are specific to each instance of the object and hold information pertinent to that particular object.

For example, in a `Car` class, the data fields might include `color`, `make`, `model`, and `year`. Each car object instantiated from the `Car` class can have different values for these fields, representing different attributes of different cars.

It's vital to define data fields prominently within a class structure, ensuring they are adequately encapsulated. Encapsulation protects data fields by restricting direct access to them, typically by making them private and using methods known as getters and setters to modify or retrieve the values.

Methods

Methods are the heart of procedural knowledge in object-oriented programming. They define the behaviors and abilities of an object, enabling it to perform specific functions within a program.

Consider the `Car` class again. Its methods might include `startEngine()`, `drive()`, and `stop()`. Each method executes a specific task, allowing the car object to interact within its environment.

When designing methods, it's essential to ensure they are concise and perform clear, logical operations. Methods can also interact with data fields to modify or retrieve data, providing a crucial link between an object's declarative and procedural knowledge. This fusion enables an object's ability to function dynamically in a program.