Trust is meta attribute to signal the trustworthy of a stream element. Its value is a double between 0 (untrustworthy) and 1 (trustworthy). In case of recovery, the trust attribute can be used to signal that an element is possible affected by a recovery process (e.g. a duplicate because of a rollback recovery). If the trust is defined as meta attribute at the source access and if a system crash occurs and Odysseus gets recovered, operators that change the trust value of elements get installed, depending on the used recovery technique:
- Gap Recovery, Stateful Gap Recovery: Elements that may have different values as in a failure-free run (e.g. different aggregation results due to missing elements) will have a decreased trust.
- Rollback Recovery, Full Replay Recovery: Elements that are possible duplicates will have a decreased trust.
- Precise Recovery: Because of the correctness guarantees, trust values are not changed.