Declaration-driven

Describing a system, process, or approach where the primary method of operation, behavior, or outcomes are determined and controlled by explicit statements, configurations, or 'declarations' rather than imperative instructions or procedural code. These declarations specify what needs to be achieved or what properties a system should possess, with the underlying implementation often handled by the system itself. This paradigm emphasizes high-level descriptions and promotes ease of configuration and modification. This often leads to greater flexibility and maintainability, allowing developers to focus on the 'what' rather than the 'how'. The execution of these declarations by the system often results in dynamic adaptations and automated processes.

Declaration-driven meaning with examples

• In a 'declaration-driven' user interface framework, the layout of the screen is defined in an XML file (the declaration) that specifies how the various elements are arranged and interconnected. The framework then automatically renders the UI based on this declaration, rather than the developer having to write a lot of code detailing this exact layout. This speeds up development.
• A modern Infrastructure-as-Code (IaC) setup is often 'declaration-driven'. Instead of writing scripts that create resources step-by-step, a configuration file declares the desired state of the infrastructure. For example, specifying 'I want 3 servers' and 'a database server' in a file. The IaC tool handles the automated provisioning of these resources.
• Consider a 'declaration-driven' state management library. A developer declares the possible states of an application and how the application should react to changes of these states. The library then automatically handles the necessary transitions and updates of data according to these declarations, minimizing boilerplate code and simplifying management.
• Think about a 'declaration-driven' data transformation system where you define the data mapping rules via declarative statements, without specifying the exact steps needed to transform the input data into the desired output format. The system itself analyzes the declaration and figures out the execution plan.