Standard Information Models

Overview

In this chapter, the base Information Model of OPC UA is introduced. This model provides the foundation for OPC UA information modeling and is always used as foundation to define additional Information Models. We will also look at the extensions of this model defined by the OPC UA specification. Those extensions are used to define a standard way to represent capabilities and diagnostic information of an OPC UA server in its Address Space and how specific information for current data, historical data, state machines, programs, alarms, and conditions are modeled. Depending on your application you should use those extensions (for example, in the case of Data Access) or you must use them (for example, in the case of Historical Data where it is required to provide certain information). Finally, we take a look at what standard Information Models are currently in development by other organizations based on OPC UA. Maybe there are already activities in your domain that you can use or should join.

Before looking at those standard Information Models, we start this chapter by considering how to handle standard Information Models. What is defined by an OPC-UA-based Information Model, how you can actually define such a model, and what mechanisms are built into OPC UA allowing servers and clients to work simultaneously with different Information Models?