ViewPoint Manual

Customizing ViewPoint
ViewPoint Manual—426801-001
6-2
Writing Custom Event-Message Filters
Writing Custom Event-Message Filters
The primary EMS filter and any optional alternate filters installed in the ViewPoint
application determine which event messages are selected for display. ViewPoint
provides two default filters on the installation subvolume: one for the Primary Events
screen and the other for the Alternate Events screen.
The default filters tell the ViewPoint application what event messages to display at the
node. Furthermore, they indicate to the ViewPoint software which event messages are
flagged by their subsystems as representing action events (events requiring operator
intervention) or potentially critical events, so that these can be highlighted as such in
the displays.
You can tailor the ViewPoint event-message displays by writing custom event-message
filters for use with any of the event presentation screens. Thus, you can arrange for
selection of only a subset of the available event messages. The EMS Manual gives full
instructions for writing filters using the EMS filter language.
The default event-message filter for the Primary Events and Last Events screens is the
same for all users of the ViewPoint application. You can write a custom filter that
differs from the default filter provided by ViewPoint and install this filter when
ViewPoint is installed, replacing the default primary-events filter. Or, you can change
the filter after ViewPoint is installed by stopping ViewPoint, changing the ViewPoint
configuration, then restarting ViewPoint. (Refer to Section 7, Installation,
Configuration, and Startup for a description of installing a new primary filter.)
If you have many messages going into the main ViewPoint console, you can separate the
application messages from the system messages by configuring a separate event
collector, besides the default, ($0), for all application messages. You will need two
consoles, one for the filtered system messages, and one for the application messages
because a ViewPoint terminal can not look at both at the same time.
Unlike the primary-events filter, the alternate-events filter that controls events sent to
Alternate Events screens can be customized from within the ViewPoint application.
There are several ways to do this.
You can write any number of alternate-events filters in addition to the default alternate-
events filter provided by ViewPoint. This allows operators to choose a particular filter
for a particular purpose. Once a custom filter exists, the operator can request that filter
by specifying its name on the Alternate Event Configuration screen. (Refer to Section 3,
Definition of ViewPoint Screens for a description of the Alternate Event Configuration
screen.)
You do not have to write a custom alternate-events filter to control the events selected or
discarded by the default filter. The default alternate-events filter contains code that
allows an operator to configure the filter dynamically by entering parameters on the
Alternate Event Configuration screen. (Refer to the subsection “Filter Parameters for
Dynamic Configuration” later in this section for more information.) In addition, when
you write your own filters, you can use the default filter as a model to include or extend
this code (see “The Default Alternate-Events Filter” later in this section for the filter
source code).
As an aid to writing custom filters, the next four subsections provide: