A rule engine is a software component that evaluates a set of declarative if-then rules against input data and executes the associated actions when conditions are met, separating business or policy logic from application code. It is a specialised form of inference engine that applies forward- or backward-chaining evaluation over a rule base rather than general-purpose reasoning. Rule engines underpin automated compliance and policy engine systems, where regulatory or organisational rules must be applied consistently and updated without redeploying software.