Glossary
In the following table the used terms and abbreviations regarding OPC UA are described.
| Term | Meaning |
| Monitored Item | If an OPC UA item was added to a subscription this is a monitored item. |
| Address space |
The collection of information that an OPC UA Server makes visible to its Clients. The OPC UA address space consists of objects , types and views folders. Views (and thus also the views folder) are not supported by the WinCC OA OPC UA server/client. |
| OPC UA attribute | A primitive characteristic of a Node. All Attributes are defined by OPC UA, and may not be defined by Clients or Servers. Attributes are the only elements in the Address Space permitted to have data values. |
| Certificate | A digitally signed data structure that describes capabilities of a Client or Server. |
| Communication stack | A layered set of software modules between the application and the hardware that provides various functions to encode, encrypt and format a Message for sending, and to decode, decrypt and unpack a Message that was received. |
| Node | The fundamental component of an Address Space. |
| Subscription | If the client wants to receive notifications on value changes or events, it has to create a subscription on the server. This subscription handles the processing of the notifications. |
| View | A specific subset of the Address Space that is of interest to the Client. |
