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- The System (Dataset Framework) wants to publish events about programs accessing datasets. Consumers for these events are the lineage writer, usage registry, and audit trail.
- The System wants to publish events about meta data changes for entities. These events will be consumed by the Tracker extension.
- The System (Scheduler) wants to trigger runs of programs (workflows) based on events; for example, availability of data, status of another program, external events, etc.
- The System (App Fabric) wants to emit notifications about the state of running programs (or their completion). This may include changes to the workflow token as execution of a workflow progresses.
- The System wants to notify programs about a change in their configuration.
- The User (Developer, DevOps) wants to receive notifications about events in the system, such as meta data changes, program state transitions, data availability, etc.
- The User (DevOps) wants to trigger programs based on custom notifications.
- The User (Developer, DevOps) wants to send control messages to all containers of a program or an app.
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