Targeting
Common contract for nodes that read from upstream sources and write to downstream targets — the executor / filter / trigger family.
Lifting these three properties out of the individual MetaData data classes lets the editor UI render a single "wire your sources and targets" panel regardless of the concrete node type, and lets cross-cutting machinery (cycle detection, dependency graphing, propagation) walk the swarm without caring which subtype it is on.
Inheritors
Properties
The set of ExecutionSources configured to wake this node. The node processor checks the incoming event against this list before doing any work. An empty list means "never auto-fire" — only manual execution.
Upstream nodes whose values feed this one. For a filter or executor this is the data being read; for a trigger it is the value being watched.
Downstream nodes this one writes to or actuates. May be empty for nodes that only side-effect outside the swarm (e.g. an SMTP executor).