By providing Methods to change the AddressSpace, using the arguments of those Methods provides the highest flexibility and is therefore the recommended approach to change the structure of the AddressSpace. The specific arguments allow, for example, to provide the full configuration of a newly added Node or set of Nodes, to define exactly which Nodes should be removed with which options, etc.

There are different patterns that can be used when using Methods. They are described in the following.

In this case, the TypeDefinition provides Methods to add or remove instances of the type.

Note that Methods can only be applied to Objects and ObjectTypes, therefore this only works with ObjectTypes, not with VariableTypes.

OPC 10000-3 already defines a standardized BrowseName to create Objects of an ObjectType, “0:Create”. It is supposed to be a class Method on the ObjectType which is called on the ObjectType to create a new instance of the ObjectType. The arguments of the Method should provide the place where to put the new Object (e.g. the parent NodeId), and the configuration of the new Object (like what optional components should be available).

The deletion of an Object can be a normal instance Method, which is called on the instance in order to delete it. As an alternative, a class Method could be used taking identification of the instance to be deleted as an input argument.

An alternative approach, taking the ownership of the instance into account, is to provide Methods to add or remove Nodes on the parent where the new Node is to be added or removed.

This is a more intuitive approach for client users as they directly experience where the new Node is added or an existing one can be removed, and from a server developer’s perspective fits better to the place where the functionality would be implemented.

Examples of this approach can be found in the PubSub configuration of OPC 10000-14. For example, the PubSubConnectionType allows you to add a WriterGroup with the AddWriteGroup Method or a ReaderGroup with a AddReaderGroup Method, and to delete them with the RemoveGroup Method. Those added groups become direct children of instances of the PubSubConnectionType. See Figure 8 for a graphical representation, taken from OPC 10000-14. A Server may have several instances of those, and the Object on which the Method is called, gives the context where an instance is added or removed.

Figure 8 – Example of Methods at the place the instance is located (taken from OPC 10000-14)

As a special case of Method calls, the standardized file transfer of OPC UA can be used to provide larger changes of the AddressSpace. This is useful, when many things need to change in the AddressSpace in one atomic operation, and not just individual instances or a small set of Nodes based on a TypeDefinition.

OPC 10000-14 provides this approach as well for larger changes of the PubSub Configuration. The PubSubConfigurationType is a subtype of the FileType defined in OPC 10000-20 and allows to either read a whole PubSubConfiguration or deploy a new configuration to the server. A specific file format is used for this case. Depending on the use case, different file formats may be used, for example, when downloading a recipe to a machine.