The Correlation ID field is used as an optional relational identifier to indicate a sequence of data records of a single data type are related, and that a group of data records across multiple data types are related. It helps to correlate events from a component with events from another components.
For example, consider a vehicle being used for a cross country trip. It is useful to label all location publishes that occur during this trip with the same correlation ID value. It is also be useful to tag any attributes that change, property publishes, alarms, and log records with a correlation ID. This would make it easier to group, aggregate, or separate the data during or after the trip.