OPC UA provides various modelling concepts (see OPC 10000-3).

• Objects structuring the AddressSpace
• Variables providing Values
• Methods that can be called by a Client and are executed by the Server
• ObjectTypes defining the semantic and structure of Objects
• VariableTypes defining the semantic and structure of Variables
• DataTypes defining the semantic and structure of Values
• Events generated by the Server that can be received by Clients
• EventTypes describing the semantic and structure of Events
• References defining relationships between Nodes
• ReferenceTypes defining the semantic of References

Based on those fundamental concepts, additional base concepts are defined like

• Conditions and Alarms as Events that are always in a state and can therefore be represented as Objects in the AddressSpace (OPC 10000-9)
• State Machines (OPC 10000-16)
• Interfaces and AddIns allowing extensibility into various ObjectType hierarchies (OPC 10000-3)
• Alias Names as searchable entry points to Nodes (OPC 10000-17)
• Dictionary References to reference external dictionaries (OPC 10000-19)

In OPC 10000-3 there is already an Annex describing how to use the modelling concepts in general, and in OPC 10000-5 there is an Annex, describing the design decisions for creating the server information (ServerType).