Specifies higher-level event types to be used as launch-on-demand event sources. Each sub-dictionary defines events for a particular event subsystem, such as "com.apple.iokit.matching", which can be used to launch jobs based on the appearance of nodes in the IORegistry. Each dictionary within the sub-dictionary specifies an event descriptor that is specified to each event subsystem. With this key, the job promises to use the xpc_set_event_stream_handler(3) API to consume events. See xpc_events(3) for more details on event sources.