Glossary · System coordination, integration and orchestration
Rules engine
Also known as: Business rules engine, Rule engine
German: Regel-Engine
In software engineering, a rules engine is a software component that evaluates a set of declarative rules (conditions and actions) against incoming data or events and executes the actions of the rules whose conditions are met, keeping decision logic separate from application code.
- System integration
In one sentence
A rules engine evaluates declarative condition-action rules against data or events and executes matching actions, separating logic from code.
Example
An MES rules engine blocks a lot automatically when two consecutive measurements exceed the warning limit and notifies the quality engineer.
How it applies
- Engineering: Rules engines let domain experts adjust decision logic (routing, alarms, quality decisions) without changing program code. Keep rules testable, versioned and reviewed like code.
- Operation: Large rule sets can interact in unexpected ways; conflicting rules and rule priorities need explicit handling and a way to see which rule fired and why.
- Change control: A rule change can change production behavior as much as a software change. Put rules under Change control, especially in regulated manufacturing.
- Documentation: Document the rules in a readable form (decision tables, rule catalog) with owner, purpose and version. Operator-facing effects of rules, such as automatic blocks, belong in the user documentation.
Rules engine vs. workflow engine
A rules engine decides: it evaluates conditions and returns or triggers actions. A Workflow engine sequences: it moves a process through defined steps over time. Workflow engines often call a rules engine at decision points.
Rules engines are not suitable for safety functions; those require deterministic, assessed implementations.