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AVEVA™ Communication Drivers

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OPC UA Item Names and Syntax

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  • Last UpdatedMar 22, 2017
  • 2 minute read

OPC UA Item Syntax

You can access data for OPC UA server items in the default namespace, with a complete namespace URI, and with a namespace alias. Each context requires its own syntax:

Namespace

Item Syntax and Description

Example

Default Namespace

UAItemReference or //UAItemReference

  • UAItemReference is the identifier of the item (complete path of the OPC UA Server item, followed by the NodeId) in OPC UA Server.

  • The UA Item Reference is resolved by the OPC UA Server, and the case is preserved. This is case sensitive

PLCport.PlCobject.N40:0

Namespace URI

UANS(UANamespaceURI),UAItemRef(UAItemReference)

  • UANS stands for UANamespace, and is a keyword.

  • UANamespaceURI is the true namespace URI in OPC UA Server.This is case sensitive.

  • UAItemRef stands for UAItemReference, and is a keyword.

  • UAItemReference is the identifier of the item (the complete path of the OPCUA Server item, followed by the NodeId) in the OPC UA Server. UA Item Reference is resolved by the OPC UA Server, and the case is preserved. This is case sensitive.

UANS(http://test.org/UA/Data/)UAItemRef(10847)

Namespace Alias

/UANamespaceAlias/UAItemReference

or

UANS(UANameSpaceAlias)UAItemRef(UAItemReference)

  • UANS stands for UANamespace, and is a keyword.

  • UANamespaceAlias is the Namespace alias name used to identify the namespace in the OPC UA Server. This is configured in the OPC UA editor. UANameSpaceAlias is replaced by the true namespace URI in UA Client, before it is sent to the server. This is case insensitive

  • UAItemRef stands for UAItemReference, and is a keyword.

  • UAItemReference is the identifier of the item (the complete path of the OPC UA Server item, followed by the NodeId) in the OPC UA Server. UA Item Reference is resolved by the OPC UA Server, and the case is preserved. This is case sensitive.

UANS(Data)UAItemRef(10847)

Using the VT Item Suffix

You can configure OPC UA data sources to use the /VT item suffix to gain better control of data access in OI Gateway. Using the /VT item suffix enables you to tell the underlying OPC UA server the type of data you want the server to report to OI Gateway.

To avoid delayed item validation, apply the /VT item suffix to an item name using the following syntax: <item name> /VT_<DataType>. For example, item1 /VT_I4.

VT Suffix Syntax Example

If you want to specify a 2-byte signed Integer (/VT_I2) as the data type for an OPC UA server path of <OPCUAServer>.Blower.Int2, the item name in OI Gateway would be subscribed as <OPCUAServer>.Blower.Int2 /VT_I2.

For information about specific VT data types, see OPC UA Data Conversion.

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