Glossary · System coordination, integration and orchestration
Time coherence
Also known as: Temporal coherence
German: Zeitkohärenz
In distributed and integrated systems, time coherence is the property that the timestamps and time references used by different components are consistent with each other, so that events recorded in different systems can be ordered and correlated correctly.
- System integration
In one sentence
Time coherence means timestamps across components are consistent, so events recorded in different systems can be ordered and correlated.
Example
Because all controllers, drives and the historian are synchronized via PTP, the sequence-of-events analysis shows that the pressure alarm came 12 ms before the valve closed.
How it applies
- Engineering: Time coherence depends on Time synchronization (NTP, PTP), consistent time zones and formats (preferably UTC) and knowing where timestamps are generated: at the sensor, the controller or the receiving server.
- Operation: Incoherent time makes root cause analysis unreliable; events can appear in the wrong order. Monitor synchronization status and flag data with unsynchronized timestamps.
- Evidence: For audit trails and safety investigations, coherent time is part of data integrity.
- Documentation: Document the time source, synchronization method, expected accuracy and timestamp conventions in the system documentation, and state the time basis of logs and reports for users.
Time coherence vs. time synchronization
Time synchronization is the mechanism that aligns clocks. Time coherence is the resulting property of the whole system's time information, which also depends on formats, time zones and where timestamps are taken.