EMS Manual

Reporting Events
EMS Manual—426909-005
8-5
Task 2: Decide What to Include in Event Messages
Both messages in the action-event pair should include the appropriate action tokens
because applications use those tokens to match the action-attention message with the
corresponding action-completion message.
Because the operator might overlook a displayed event message or, rarely, an event
message might be lost, your subsystem should reissue any action-attention event that
has not been remedied within an appropriate period of time. Applications retrieving
action events should treat an identical copy of a currently outstanding action-attention
message as if it were an action-completion message for the previous issuance of that
action-attention message. (That is, the old copy should be made inactive by the new
copy so that only one copy of the action event is active at a time.)
Task 2: Decide What to Include in Event
Messages
Event messages are based on tokens and are built in a standard manner by the EMS
routines as described in Section 15, EMS Procedures.
The EMS routines require that many common event-message components be passed
as parameters, ensuring that all event messages have at least the basic facts.
However, a lot of room remains for subsystem variation in event messages. This
subsection describes:

Information automatically provided for you when the event message is initialized

Components you are required to include in event messages

Components you can optionally include in event messages
General Guidelines
When designing how your subsystem will report events, remember a few basic
principles:

Because any event message has two possible audiences—applications and
operators—it is important that the message convey meaningful information to both
audiences. The tokenized information should contain a complete description of the
event for applications, and the text should summarize the event for operators.

The event messages should be self-contained, each fully describing a particular
event, for these reasons:

Because you cannot ensure that a filter that retrieved a particular event
message would retrieve the continuation event message (if there were one), do
not depend on a second message to carry additional information about the
same event to the same recipient.

Because the operator or application might have to take remedial action based
only on the information in the message, include everything the recipient needs
in order to respond with an appropriate interactive or programmatic command.