A vendor that is developing an OPC UA application, shall review the list of available Profiles. From this list the vendor shall select the Profiles that include the functionality required by the application. Conformance to a single Profile may not yield a complete application. In most cases multiple Profiles are needed to yield a useful application. All UA applications shall support at least one Application Profile.

For example an HMI Client application may choose to support the Minimum UA Client 2022 Profile, the “Data Access Client Facet”, the “DataChange Subscriber Client Facet” and the “Attribute Write Client Facet”. This list of Profiles would allow the Client to communicate with an OPC UA Server using UA-TCP/UA Security/UA Binary. It would be able to subscribe for data, write to data and would support the DA data model.

Clients should take into account the types of Servers and Server Profiles that they are targeted to support. Some Servers might not support Subscriptions and Clients should be able to fall back to the Read Service.

A special case is a generic Client that is designed to communicate with a large number of Servers and therefore able to perform a broad range of functionality. ”Standard UA Client Profile” has been defined for this kind of Clients.

Many Clients, however, will be specialized and do not need all of the functionality in the ”Standard UA Client Profile” and thus would only support the limited set of functionality they require. A trend Client, for example, would only need functionality to subscribe to or read data.