Hello,

You can think of the method concept as basically the same as method in object-oriented programming. Methods must belong to an Object (or ObjectType) and methods can only be invoked on Objects (or ObjectTypes) referencing the Method with a HasComponent Reference.

A method in OPC UA is called by a client and returns a result. Each method specifies the input arguments a client shall use and the output arguments a client shall expect as a result. The client uses the call service to invoke the method and the response of this service call contains the result of the method. Possible examples of methods could be a method to open a valve or to start a motor, as well as more complex tasks like calculating some simulation results based on provided input values. In general, using a method makes sense when a set of arguments is used as input or output or both or a special action should be triggered in a defined way in the server.

In Prosys OPC UA Java SDK, SampleConsoleServer contains an example method MyMethod. The MyMethod can be called in the context of MyDevice object. The MyDevice is available by browsing Objects/MyObjects/MyDevice. For discussion on how to handle methods in Prosys OPC UA Java SDK, see chapter 7 “Method Manager” of the Server Tutorial.

Oh ok,

I think I misunderstood the first question. According to our understanding, typically some kind of “control-logic” would call the OPC UA methods.

However, there’s no specific examples published that we know of, so this answer may not have much benefit for you.