This clause specifies the OPC UA Services. The OPC UA Servicedefinitions are abstract descriptions and do not represent a specification for implementation. The mapping between the abstract descriptions and the Communication Stackderived from these Servicesare defined in OPC 10000-6. In the case of an implementation as web services, the OPC UA Servicescorrespond to the web service and an OPC UA Servicecorresponds to an operation of the web service.
These Servicesare organised into Service Sets. Each Service Setdefines a set of related Services. The organisation in Service Setsis a logical grouping used in this standard and is not used in the implementation.
The Discovery Service Set, illustrated in Figure 1, defines Servicesthat allow a Clientto discover the Endpointsimplemented by a Serverand to read the security configuration for each of those Endpoints.
The SecureChannel Service Set, illustrated in Figure 2, defines Servicesthat allow a Clientto establish a communication channel to ensure the Confidentialityand Integrityof Messagesexchanged with the Server.
The View Service Set, illustrated in Figure 5, defines Servicesthat allow Clientsto browse through the AddressSpaceor subsets of the AddressSpacecalled Views. The Query Service Setallows Clientsto get a subset of data from the AddressSpaceor the View.
The Attribute Service Setis illustrated in Figure 6. It defines Servicesthat allow Clientsto read and write Attributesof Nodes, including their historical values. Since the value of a Variableis modelled as an Attribute, these Servicesallow Clientsto read and write the values of Variables.
The Method Service Setis illustrated in Figure 7. It defines Servicesthat allow Clientsto call methods. Methods run to completion when called. They may be called with method-specific input parameters and may return method-specific output parameters.
The Subscription Service Setdefines Servicesthat allow Clientsto create, modify and delete Subscriptions. Subscriptionssend Notificationsgenerated by MonitoredItemsto the Client. Subscription Servicesalso provide for Clientrecovery from missed Messagesand communication failures.