What defines an Appian 'Expression Rule'?

An Appian 'Expression Rule' is defined as a reusable piece of logic or calculation. This means that expression rules can be created to encapsulate complex logic or calculations that can be utilized across different components or applications within Appian. By having this reusable logic, developers can maintain consistency, reduce redundancy, and streamline updates since they only need to change the logic in one place if modifications are necessary.

Expression rules are versatile and can handle various scenarios, such as performing mathematical calculations, processing data, or manipulating strings, making them essential tools for creating dynamic and efficient applications in Appian. Their reusability also contributes significantly to the maintainability and scalability of Appian projects.