The chapter discusses the importance and benefits of object-oriented application frameworks in modern software development. It highlights that while computing power and network bandwidth have increased, the design and implementation of complex software remain costly and error-prone due to the continuous reinvention of core concepts and components. Object-oriented application frameworks are proposed as a solution to reduce these costs and improve software quality by providing reusable, modular, and extensible solutions. Key benefits of frameworks include: - **Modularity**: Encapsulating implementation details behind stable interfaces. - **Reusability**: Defining generic components that can be applied to create new applications. - **Extensibility**: Providing explicit hook methods for customization. - **Inversion of Control**: Allowing application-specific processing through event handlers. The chapter also outlines the classification of frameworks based on their scope, such as system infrastructure frameworks, middleware integration frameworks, and enterprise application frameworks. It discusses the strengths and weaknesses of frameworks, emphasizing the need for effective learning curves, integration, and maintainability. Future trends in framework development are expected to focus on reducing development effort, developing domain-specific enterprise frameworks, and advancing black-box frameworks. The chapter concludes by highlighting the importance of standards and documentation in ensuring the success and widespread adoption of frameworks.The chapter discusses the importance and benefits of object-oriented application frameworks in modern software development. It highlights that while computing power and network bandwidth have increased, the design and implementation of complex software remain costly and error-prone due to the continuous reinvention of core concepts and components. Object-oriented application frameworks are proposed as a solution to reduce these costs and improve software quality by providing reusable, modular, and extensible solutions. Key benefits of frameworks include: - **Modularity**: Encapsulating implementation details behind stable interfaces. - **Reusability**: Defining generic components that can be applied to create new applications. - **Extensibility**: Providing explicit hook methods for customization. - **Inversion of Control**: Allowing application-specific processing through event handlers. The chapter also outlines the classification of frameworks based on their scope, such as system infrastructure frameworks, middleware integration frameworks, and enterprise application frameworks. It discusses the strengths and weaknesses of frameworks, emphasizing the need for effective learning curves, integration, and maintainability. Future trends in framework development are expected to focus on reducing development effort, developing domain-specific enterprise frameworks, and advancing black-box frameworks. The chapter concludes by highlighting the importance of standards and documentation in ensuring the success and widespread adoption of frameworks.