A business logic layer (BLL) is a separate code base from the data and presentation layers that contains business logic, including calculations and business objects. Using a BLL in a multi-tier architecture supports modular design, code reusability, and easier code maintenance. Implementing application versions can also be easier, and development teams can specialize in different skills. A web application example is an insurance company’s website, where the BLL determines which policies a customer can see. The same benefits apply to traditional software application development.
In the practice of information system logical architecture, a business logic layer (BLL) consists of business logic contained in a separate code base from the data layer and the presentation or graphical user interface layer. Business logic can include not only calculations, but can also represent business objects such as products or employees. It will provide methods for accessing and maintaining data and may allow work to be moved from one function to another. In addition, the BLL defines other business rules. It is also known as the domain layer, as it contains business or domain logic.
Using a business logic layer is a recommended convention for software engineering. Building a business logic layer together with a data and presentation layer in a multi-tier architecture supports modular design and code reusability. There are many benefits to compartmentalizing an application into multiple tiers.
One of the benefits of the multi-level architecture is easier code maintenance. As business requirements change, the BLL may be the only area that requires code changes. When compartmentalized design is not used, it can be unclear where in the application the business logic code changes need to be made.
Another benefit is that implementing application versions can be easier. In cases where only the BLL has been updated, this is the only component that needs to be released into the production environment. The data tier and presentation tier can remain unchanged.
Development teams could also benefit from using a BLL and multi-level architecture. Staff members may specialize in data, business logic, or presentation development skills and can learn their part of the application more quickly. The work in each level can be done simultaneously, which can compress the overall development time frame.
Using a BLL and supporting data and presentation layers is important in web applications. As an example of a web application that uses a layered architecture, an insurance company’s website might host an application where customers can view their insurance policies. Customers use a web browser to visit the website, and the browser interacts with the presentation layer code of the application. The customer’s policy details are held in a database; this is the data layer. The application code that determines which policies a customer is entitled to see, and any calculations or business logic applied to that data are hosted in the BLL.
The multi-layered architecture, with a compartmentalized business logic layer, can be used in traditional software application development and web application development. The system architecture of the traditional software application will be similar to that of the web application. You will also realize the same benefits.
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