The development of OPC UA client applications is considerably more complex than clients for earlier OPC specifications.

• The client may have to support multiple communications stacks in order to be able to access many different OPC UA servers.
• A secure server access session has to be established
• The capabilities and its data structure needs to be determined and the client needs to be able to work with differently structures servers.

Some if the complicating elements can be handled in components but this simplifies on the software development. The product documentation, testing and the customer support has to cover all aspects.

The UA server network database allows complex structures and gives the server developer the possibility to map the device data in many different ways into the server database. Browsing the OPC UA server to find the proper items and item attributes can be a challenge. The network structure cannot be easily put into a two dimensional presentation. The OPC UA server can define Views with a subset of the network structure but such Views will be different in each server. More training and support will be required for client application configurators.