Message types

Open Message Format (OMF) message types have the following categories:

• type

• container

• data

Each message type creates a different type of data within the PI System and contains keywords that define characteristics of the data. Most of the message types are used to create the structure of the data and give it meaning. Dynamic data messages contain time-series data for which the PI System is known. The message types, their keywords, and the data they create are described in detail in this section.

The OMF application should send each message only once. Types, containers, static data, and links should be sent when the OMF application is started for the first time to create the structure of the data. Under normal circumstances, the OMF application should not re-transmit this information every time it is restarted. PI Web API stores the necessary information in its cache to successfully receive data values. The OMF application should send new dynamic data messages as the data is created, because dynamic data messages create the stream of data into Data Archive. To prevent duplicate data, each unique dynamic data message should only be sent once.