## 3 Puzzle Pattern Conceptualization
### Implementing Puzzle Pattern  
The primary idea behind the Puzzle Pattern is to develop code within these interfaces, the puzzle pieces. Concrete classes--or the puzzle boards--are then assembled by implementing these interfaces. This method of organizing software components enhances modularity and encourages the development of maintainable and scalable software systems. Each interface mandates a behavior through its methods, using abstract methods to outline the necessary services or state required from the concrete class. In other words, each abstract method in an interface simply returns the instance needed to provide the functionality required in the concrete methods of that interface. This state or functionality is provided by the concrete class that implements the interface, exploiting the state implemented by itself. This approach not only facilitates a clear division of responsibilities but also enhances the system's adaptability by allowing individual components to be developed, tested, and maintained independently. By fostering a modular design, the Puzzle Pattern promotes a structure where the integration of new functionality or the modification of existing features becomes more manageable, mirroring the way puzzle pieces can be individually added or replaced without disrupting the entire system. Let us consider a simplistic example in which the aim is to implement a Java service that is responsible for handling digitalized documents. The OOM that represents documents is already defined (the class Document is defined by a content, a timestamp, and a type), as well as the DatabaseService that is responsible for database interactions. Two functionalities need to be implemented: the document deletion and the document acquisition. The approach to follow is the following one:  
1. Define one puzzle piece for each functionality that needs to be implemented. 2. Implement the behavior of each puzzle piece. If the single puzzle piece needs to rely on further functionalities, in this scenario, the DatabaseService, then declare abstract \"getters\" methods that are responsible for those third-party services provisioning. 3. Assemble the \"board\" by defining a concrete class that implements all the puzzle pieces needed. The implementation of the Document Management System using the Puzzle Pattern approach, as depicted in the provided UML diagram (Figure 1) and subsequent Java code \(1\) in Appendix A, offers a clear demonstration of how to architect software to promote modularity and loose coupling. By segregating different functionalities such as the acquisition and deletion of documents into separate interfaces, the system achieves a high level of modularity. This separation allows for distinct behaviors to be developed, tested, and maintained independently of one another, enhancing the system's manageability and scalability. Implementing functionalities as interchangeable puzzle pieces (interfaces) enables easier adjustments and additions down the line. For instance, introducing a new operation, such as document modification, can be done by adding another interface and implementing it in the DocumentService class or a new class altogether without disrupting existing code. The design promotes reusability through interfaces. Different parts of the application can reuse the same interface for similar operations, or new projects can adopt the established interfaces, reducing the need to rewrite common functionality. The interfaces ensure that concrete implementations are loosely coupled, minimizing the impact of modifications on other parts of the system and easing maintenance. While the system promotes modularity and flexibility, it also introduces additional complexity. Developers must understand how interfaces interact and ensure that concrete classes correctly implement all required interfaces. This learning curve might slow down initial development, especially for teams unfamiliar with interface-driven designs.