Web Application Technology Structure

To make the structure of a web application works a little clearer, a typical technology stack is illustrated here. 

Data: the core data of the system will be stored in a database comprising a number of tables. Data can be validated at this level, but business rules are not implemented at this layer. This can be thought of as the ‘warehouse’ or ‘memory’ part of the solution

Business Logic Layer: this part of the stack reflects the requirements in the functional and technical specification to ensure the solution functions as required. This can be thought of as the ‘brain’ part of the solution

UI Layer: the UI (User Interface) is what the user ‘sees’ and interacts with when accessing the solution

Presentation Layer Business Logic: this part of the UI governs how the data is presented to the user. It is not as complex as the business logic layer, but can do some of the simple ‘thinking’ without communicating with the ‘brain’. The UI can be thought of as the ‘shop window’ or ‘face’ of the solution

Back-end: the data and business logic layers are often called the ‘back-end’ – users do not directly access or see these parts of a system

Front-end: the UI is often called the ‘front-end’ – it is what the user sees of the system

See also: CMS Technology Stack