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A DAIS::AlarmsAndEvents::Subscription::Manager is an object holding a filter specification set up by a client. The filter
is used to specify what notifications shall be sent to the client. A server can support various filter functions and a client
can ask the DAIS::AlarmsAndEvents::Subscription::IHome object what filter functions are supported. The subscription home is
also used to create any number of subscription manager objects. Each subscription manager shall be associated with a client
implemented callback object so that the server can send alarm and event notifications to the client.
A server may optionally support an event history. The event history shall record all alarms and events appearing in a server.
The method async_read_history() gives clients access to the event history. The size of the event history is server specific
and outside the control of a client.
In OPC the Subscription interface corresponds to the interface IOPCEventSubscription.
Figure 5-5 DAIS alarms and events subscription IDL in UML