3 Terms, definitions, and conventions ToC Previous Next

3.1 Use of terms ToC Previous Next

Defined terms of OPC UA specifications, types and their components defined in OPC UA specifications and in this specification are highlighted with italic in this document.

Certain Ethernet POWERLINK related terms and names are used together with POWERLINK, especially in cases where the terms might lead to naming conflicts with existing OPCUA terms. For instance the term Managing Node (a device role in POWERLINK) contains the word Node that has a different meaning in OPC UA.

Table 1 contains a list with the most prominent examples for common terms that have different meanings in OPC UA and POWERLINK.

Table 1 – Common terms with different meanings

Term OPC UA POWERLINK
Node OPC 10000-1:
The fundamental component of an AddressSpace.
Commonly used for physical devices in a POWERLINK network.
Terms:
POWERLINK Device
POWERLINK Controlled Node
POWERLINK Managing Node
NodeId OPC 10000-3:
Nodes are unambiguously identified using a constructed identifier called the NodeId.
Each POWERLINK Device (MN, CN and Router) is addressed by an 8 bit POWERLINK Node ID on the POWERLINK layer. This ID has only local significance (i.e. it is unique within a POWERLINK segment) and addresses a physical device whereas the NodeId of OPC UA addresses elements of the internal object dictionary.
Object OPC 10000-3:
Objects and their components are represented in the AddressSpace as a set of Nodes described by Attributes and interconnected by References.
Data object:
   Element of the POWERLINK Object Dictionary
Process data object:
   Object for isochronous data exchange between
   POWERLINK Devices.
Service data object:
   Peer to peer communication with access to the
   POWERLINK Object Dictionary   of a device.
Mapping OPC 10000-6:
Specifies how to implement an OPC UA feature with a specific technology.

Note: For example, the OPC UA Binary Encoding is a Mapping that specifies how to serialise OPC UA data structures as sequences of bytes.
Selection of the POWERLINK Objects that are sent or received via PDOs.

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