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5.2 Introduction to OPC Unified Architecture ToC Previous Next

5.2.4 RelativePath ToC Previous Next

A RelativePath is a structure that describes a sequence of References and Nodes to follow. Annex A of OPC Part 4 Services describes a text format for a RelativePath that can be used in documentation or in files used to store configuration information.

The components of a RelativePath text format are specified in Table 11.

Table 11 – RelativePath

Symbol Meaning
/ The forward slash character indicates that the Server is to follow any subtype of HierarchicalReferences.
. The period (dot) character indicates that the Server is to follow any subtype of a Aggregates ReferenceType.
<[#!ns:]ReferenceType> A 0:String delimited by the ‘<’ and ‘>’ symbols specifies the BrowseName of a ReferenceType to follow. By default, any References of the subtypes the ReferenceType are followed as well. A ‘#’ placed in front of the BrowseName indicates that subtypes should not be followed.
A ‘!’ in front of the BrowseName is used to indicate that the inverse Reference should be followed.
The BrowseName may be qualified with a namespace index (indicated by a numeric prefix followed by a colon). This namespace index is used specify the namespace component of the BrowseName for the ReferenceType. If the namespace prefix is omitted then namespace index 0 is used.
[ns:]BrowseName A 0:String that follows a ‘/’, ‘.’ or ‘>’ symbol specifies the BrowseName of a target Node to return or follow. This BrowseName may be prefixed by its namespace index. If the namespace prefix is omitted then namespace index 0 is used.
Omitting the final BrowseName from a path is equivalent to a wildcard operation that matches all Nodes which are the target of the Reference specified by the path.
& The & sign character is the escape character. It is used to specify reserved characters that appear within a BrowseName. A reserved character is escaped by inserting the ‘&’ in front of it. Examples of BrowseNames with escaped characters are:
Received browse path name Resolves to
“&/Name_1” “/Name_1”
“&.Name_2” “.Name_2”
“&:Name_3” “:Name_3”
“&&Name_4” “&Name_4”

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