About message triggers

The message trigger determines the frequency and conditions under which a message is sent to the publish target. There are two types of triggers, one based on a time interval and the other based on changes to the key values. All key values must be PI point attributes. These options are displayed in the screen shot below.

• 1. Message trigger based on time

• 2. Message trigger based on a change in the data values

The sections below describe how to use these options.

Trigger a message at regular time intervals

You can set a time interval between 30 seconds and up to 12 months. A message is sent at the time interval specified, independent of whether there are any changes to the data. Views with this type of message trigger are called scheduled streaming views.

Note: Depending on message size and buffers, there can be a delay in when the data is received in the target. Edge-to-edge latency, the interval between when a value arrives in the PI System and when it arrives in the target system, can be greater than the interval between message triggers.

Identify the keys that trigger the message

You can decide which key changes will trigger a message. Views with this type of message trigger are called key-value-triggered streaming views. In the screen shot below, two keys which correspond to PI tags, Zone1.PWR and Zone1.RollingCost, are selected.

Once you identify the keys, you can further customize the conditions under which a message is triggered.

These choices are described below.

Trigger a message when any key value changes

The first option is to trigger a message whenever the data for any of the selected keys changes.

The following is a graphical representation of this option. It displays two keys, Key A and Key B. Messages are triggered whenever there is a change to any one of the keys, indicated by the dots. Messages are sent at t1, t2, t3, t4, and t5, as indicated by the check marks.

Trigger a message only when all key values change

The second option is to have a message sent only when the values of all keys have changed.

The following graph illustrates this. Three messages are sent at t2, t4, and t7. The green dots indicate which changed values are recorded. The value at t5 is not sent, as indicated by the empty dot.

Type of data that triggers the message

In addition to identifying the most critical data to focus on, you can also specify if you want to use archive or snapshot values to trigger the message.