4tier

4tier refers to a software architecture pattern that divides an application into four distinct logical and physical layers. This layered approach promotes modularity, scalability, and maintainability of complex software systems. The four layers typically include the presentation layer, the application layer, the data access layer, and the database layer.

The presentation layer, often referred to as the client tier, is responsible for user interface and user interaction. It is what the end-user directly sees and interacts with, such as a web browser or a desktop application. This layer communicates with the application layer to request data or trigger actions.

The application layer, also known as the business logic or middle tier, contains the core business logic of the application. It processes user requests from the presentation layer, performs calculations, and orchestrates interactions with the data access layer. This layer ensures that business rules are enforced consistently.

The data access layer acts as an intermediary between the application layer and the database. It is responsible for abstracting the details of data storage and retrieval, providing a clean interface for the application layer to access data without needing to know the specifics of the database system.

Finally, the database layer, or data tier, is where the application's data is stored and managed. This typically involves a relational database management system (RDBMS) or other data storage solutions. The data access layer interacts with this tier to perform operations like querying, inserting, updating, and deleting data. This separation allows for independent development and scaling of each tier.