Clients use the browse Services of the View Service Set to navigate through the AddressSpace or through a View which is a subset of the AddressSpace.
A View is a subset of the AddressSpace created by the Server. Future versions of this document may also define services to create Client-defined Views. See OPC 10000-5 for a description of the organization of views in the AddressSpace.
This Service is used to discover the References of a specified Node. The browse can be further limited by the use of a View. This Browse Service also supports a primitive filtering capability.
In some cases it may take longer than the Client timeout hint to process all nodes to browse. In this case the Server may return zero results with a continuation point for the affected nodes before the timeout expires.
Table 34 defines the parameters for the Service.
Table 34 – Browse Service Parameters
|
Name |
Type |
Description |
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Request |
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requestHeader |
RequestHeader |
Common request parameters (see 7.33 for RequestHeader definition). |
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View |
ViewDescription |
Description of the View to browse (see 7.45 for ViewDescription definition). An empty ViewDescription value indicates the entire AddressSpace. Use of the empty ViewDescription value causes all References of the nodesToBrowse to be returned. Use of any other View causes only the References of the nodesToBrowse that are defined for that View to be returned. |
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requestedMax ReferencesPerNode |
Counter |
Indicates the maximum number of references to return for each starting Node specified in the request. The value 0 indicates that the Client is imposing no limitation (see 7.8 for Counter definition). |
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nodesToBrowse [] |
BrowseDescription |
A list of nodes to Browse. This structure is defined in-line with the following indented items. |
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nodeId |
NodeId |
NodeId of the Node to be browsed. If a view is provided, it shall include this Node. |
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browseDirection |
Enum BrowseDirection |
An enumeration that specifies the direction of References to follow. The enumeration is defined in 7.5. The returned References do indicate the direction the Server followed in the isForward parameter of the ReferenceDescription. Symmetric References are always considered to be in forward direction therefore the isForward flag is always set to TRUE and symmetric References are not returned if browseDirection is set to INVERSE. |
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referenceTypeId |
NodeId |
Specifies the NodeId of the ReferenceType to follow. Only instances of this ReferenceType or its subtypes are returned. If not specified then all References are returned and includeSubtypes is ignored. |
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includeSubtypes |
Boolean |
Indicates whether subtypes of the ReferenceType should be included in the browse. If TRUE, then instances of referenceTypeId and all of its subtypes are returned. |
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nodeClassMask |
UInt32 |
Specifies the NodeClasses of the TargetNodes. Only TargetNodes with the selected NodeClasses are returned. The NodeClasses are assigned the following bits:
If set to zero, then all NodeClasses are returned. If the NodeClass is unknown for a remote Node, the nodeClassMask is ignored. |
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resultMask |
UInt32 |
Specifies the fields in the ReferenceDescription structure that should be returned. The fields are assigned the following bits:
The ReferenceDescription type is defined in 7.30. |
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Response |
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responseHeader |
Response Header |
Common response parameters (see 7.34 for ResponseHeader definition). |
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results [] |
BrowseResult |
A list of BrowseResults. The size and order of the list matches the size and order of the nodesToBrowse specified in the request. The BrowseResult type is defined in 7.6. |
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diagnosticInfos [] |
Diagnostic Info |
List of diagnostic information for the results (see 7.12 for DiagnosticInfo definition). The size and order of the list matches the size and order of the results response parameter. This list is empty if diagnostics information was not requested in the request header or if no diagnostic information was encountered in processing of the request. |
Table 35 defines the Service results specific to this Service. Common StatusCodes are defined in Table 182.
Table 35 – Browse Service Result Codes
|
Symbolic Id |
Description |
|
Bad_ViewIdUnknown |
See Table 182 for the description of this result code. |
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Bad_ViewTimestampInvalid |
See Table 182 for the description of this result code. |
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Bad_ViewParameterMismatchInvalid |
See Table 182 for the description of this result code. |
|
Bad_ViewVersionInvalid |
See Table 182 for the description of this result code. |
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Bad_NothingToDo |
See Table 182 for the description of this result code. |
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Bad_TooManyOperations |
See Table 182 for the description of this result code. |
Table 36 defines values for the results parameter that are specific to this Service. Common StatusCodes are defined in Table 183.
Table 36 – Browse Operation Level Result Codes
|
Symbolic Id |
Description |
|
Bad_NodeIdInvalid |
See Table 183 for the description of this result code. |
|
Bad_NodeIdUnknown |
See Table 183 for the description of this result code. |
|
Bad_ReferenceTypeIdInvalid |
See Table 183 for the description of this result code. |
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Bad_BrowseDirectionInvalid |
See Table 183 for the description of this result code. |
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Bad_NodeNotInView |
See Table 183 for the description of this result code. |
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Bad_NoContinuationPoints |
See Table 183 for the description of this result code. |
|
Uncertain_NotAllNodesAvailable |
Browse results may be incomplete because of the unavailability of a subsystem. |
This Service is used to request the next set of Browse or BrowseNext response information that is too large to be sent in a single response. “Too large” in this context means that the Server is not able to return a larger response or that the number of results to return exceeds the maximum number of results to return that was specified by the Client in the original Browse request. The BrowseNext shall be submitted on the same Session that was used to submit the Browse or BrowseNext that is being continued.
Table 37 defines the parameters for the Service.
Table 37 – BrowseNext Service Parameters
|
Name |
Type |
Description |
|
Request |
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requestHeader |
Request Header |
Common request parameters (see 7.33 for RequestHeader definition). |
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releaseContinuationPoints |
Boolean |
A Boolean parameter with the following values: TRUEpassed continuationPoints shall be reset to free resources in the Server. The continuation points are released and the results and diagnosticInfos arrays are empty. FALSEpassed continuationPoints shall be used to get the next set of browse information. A Client shall always use the continuation point returned by a Browse or BrowseNext response to free the resources for the continuation point in the Server. If the Client does not want to get the next set of browse information, BrowseNext shall be called with this parameter set to TRUE. |
|
continuationPoints [] |
Continuation Point |
A list of Server-defined opaque values that represent continuation points. The value for a continuation point was returned to the Client in a previous Browse or BrowseNext response. These values are used to identify the previously processed Browse or BrowseNext request that is being continued and the point in the result set from which the browse response is to continue. Clients may mix continuation points from different Browse or BrowseNext responses. The ContinuationPoint type is described in 7.9. |
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Response |
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responseHeader |
Response Header |
Common response parameters (see 7.34 for ResponseHeader definition). |
|
results [] |
BrowseResult |
A list of references that met the criteria specified in the original Browse request. The size and order of this list matches the size and order of the continuationPoints request parameter. The BrowseResult type is defined in 7.6. |
|
diagnosticInfos [] |
Diagnostic Info |
List of diagnostic information for the results (see 7.12 for DiagnosticInfo definition). The size and order of the list matches the size and order of the results response parameter. This list is empty if diagnostics information was not requested in the request header or if no diagnostic information was encountered in processing of the request. |
Table 38 defines the Service results specific to this Service. Common StatusCodes are defined in Table 182.
Table 38 – BrowseNext Service Result Codes
|
Symbolic Id |
Description |
|
Bad_NothingToDo |
See Table 182 for the description of this result code. |
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Bad_TooManyOperations |
See Table 182 for the description of this result code. |
Table 39 defines values for the results parameter that are specific to this Service. Common StatusCodes are defined in Table 183.
Table 39 – BrowseNext Operation Level Result Codes
|
Symbolic Id |
Description |
|
Bad_NodeIdInvalid |
See Table 183 for the description of this result code. |
|
Bad_NodeIdUnknown |
See Table 183 for the description of this result code. |
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Bad_ReferenceTypeIdInvalid |
See Table 183 for the description of this result code. |
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Bad_BrowseDirectionInvalid |
See Table 183 for the description of this result code. |
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Bad_NodeNotInView |
See Table 183 for the description of this result code. |
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Bad_ContinuationPointInvalid |
See Table 183 for the description of this result code. |
This Service is used to request that the Server translates one or more browse paths to NodeIds. Each browse path is constructed of a starting Node and a RelativePath. The specified starting Node identifies the Node from which the RelativePath is based. The RelativePath contains a sequence of ReferenceTypes and BrowseNames.
One purpose of this Service is to allow programming against type definitions. Since BrowseNames shall be unique in the context of type definitions, a Client may create a browse path that is valid for a type definition and use this path on instances of the type. For example, an ObjectType “Boiler” may have a “HeatSensor” Variable as InstanceDeclaration. A graphical element programmed against the “Boiler” may need to display the Value of the “HeatSensor”. If the graphical element would be called on “Boiler1”, an instance of “Boiler”, it would need to call this Service specifying the NodeId of “Boiler1” as starting Node and the BrowseName of the “HeatSensor” as browse path. The Service would return the NodeId of the “HeatSensor” of “Boiler1” and the graphical element could subscribe to its Value Attribute.
If a Node has multiple targets with the same BrowseName, the Server shall return a list of NodeIds. However, since one of the main purposes of this Service is to support programming against type definitions, the NodeId of the Node based on the type definition of the starting Node is returned as the first NodeId in the list.
Table 40 defines the parameters for the Service.
Table 40 – TranslateBrowsePathsToNodeIds Service Parameters
|
Name |
Type |
Description |
|
Request |
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|
requestHeader |
RequestHeader |
Common request parameters (see 7.33 for RequestHeader definition). |
|
browsePaths [] |
BrowsePath |
List of browse paths for which NodeIds are being requested. This structure is defined in-line with the following indented items. |
|
startingNode |
NodeId |
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relativePath |
RelativePath |
The path to follow from the startingNode. The last element in the relativePath shall always have a targetName specified. This further restricts the definition of the RelativePath type. The Server shall return Bad_BrowseNameInvalid if the targetName is missing. The RelativePath structure is defined in 7.31. |
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Response |
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responseHeader |
ResponseHeader |
Common response parameters (see 7.34 for ResponseHeader definition). |
|
results [] |
BrowsePathResult |
List of results for the list of browse paths. The size and order of the list matches the size and order of the browsePaths request parameter. This structure is defined in-line with the following indented items. |
|
statusCode |
StatusCode |
StatusCode for the browse path (see 7.39 for StatusCode definition). |
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targets [] |
BrowsePathTarget
|
List of targets for the relativePath from the startingNode. This structure is defined in-line with the following indented items. A Server may encounter a Reference to a Node in another Server which it cannot follow while it is processing the RelativePath. If this happens the Server returns the NodeId of the external Node and sets the remainingPathIndex parameter to indicate which RelativePath elements still need to be processed. To complete the operation the Client shall connect to the other Server and call this service again using the target as the startingNode and the unprocessed elements as the relativePath. |
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targetId |
ExpandedNodeId |
The identifier for a target of the RelativePath. |
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remainingPathIndex |
Index |
The index of the first unprocessed element in the RelativePath. This value shall be equal to the maximum value of Index data type if all elements were processed (see 7.18 for Index definition). |
|
diagnosticInfos [] |
DiagnosticInfo |
List of diagnostic information for the list of browse paths (see 7.12 for DiagnosticInfo definition). The size and order of the list matches the size and order of the browsePaths request parameter. This list is empty if diagnostics information was not requested in the request header or if no diagnostic information was encountered in processing of the request. |
Table 41 defines the Service results specific to this Service. Common StatusCodes are defined in 7.39.
Table 41 – TranslateBrowsePathsToNodeIds Service Result Codes
|
Symbolic Id |
Description |
|
Bad_NothingToDo |
See Table 182 for the description of this result code. |
|
Bad_TooManyOperations |
See Table 182 for the description of this result code. |
Table 42 defines values for the operation level statusCode parameters that are specific to this Service. Common StatusCodes are defined in Table 183.
Table 42 – TranslateBrowsePathsToNodeIds Operation Level Result Codes
|
Symbolic Id |
Description |
|
Bad_NodeIdInvalid |
See Table 183 for the description of this result code. |
|
Bad_NodeIdUnknown |
See Table 183 for the description of this result code. |
|
Bad_NothingToDo |
See Table 182 for the description of this result code. This code indicates that the relativePath contained an empty list. |
|
Bad_BrowseNameInvalid |
See Table 183 for the description of this result code. This code indicates that a TargetName was missing in a RelativePath. |
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Uncertain_ReferenceOutOfServer |
The path element has targets which are in another Server. |
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Bad_TooManyMatches |
The requested operation has too many matches to return. Users should use queries for large result sets. Servers should allow at least 10 matches before returning this error code. |
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Bad_QueryTooComplex |
The requested operation requires too many resources in the Server. |
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Bad_NoMatch |
The requested relativePath cannot be resolved to a target to return. |
A Server often has no direct access to the information that it manages. Variables or services might be in underlying systems where additional effort is required to establish a connection to these systems. The RegisterNodes Service can be used by Clients to register the Nodes that they know they will access repeatedly (e.g. Write, Call). It allows Servers to set up anything needed so that the access operations will be more efficient. Clients can expect performance improvements when using registered NodeIds, but the optimization measures are vendor-specific. For Variable Nodes Servers shall concentrate their optimization efforts on the Value Attribute.
Registered NodeIds are only guaranteed to be valid within the current Session. Clients shall unregister unneeded Ids immediately to free up resources.
RegisterNodes does not validate the NodeIds from the request. Servers will simply copy unknown NodeIds in the response. Structural NodeId errors (size violations, invalid id types) will cause the complete Service to fail.
For the purpose of Auditing, Servers shall not use the registered NodeIds but only the canonical NodeIds which is the value of the NodeId Attribute.
Table 43 defines the parameters for the Service.
Table 43 – RegisterNodes Service Parameters
|
Name |
Type |
Description |
|
Request |
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|
requestHeader |
Request Header |
Common request parameters (see 7.33 for RequestHeader definition). |
|
nodesToRegister [] |
NodeId |
List of NodeIds to register that the Client has retrieved through browsing, querying or in some other manner. |
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Response |
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responseHeader |
Response Header |
Common response parameters (see 7.34 for ResponseHeader definition). |
|
registeredNodeIds [] |
NodeId |
A list of NodeIds which the Client shall use for subsequent access operations. The size and order of this list matches the size and order of the nodesToRegister request parameter. The Server may return the NodeId from the request or a new (an alias) NodeId. It is recommended that the Server return a numeric NodeIds for aliasing. In case no optimization is supported for a Node, the Server shall return the NodeId from the request. |
Table 44 defines the Service results specific to this Service. Common StatusCodes are defined in Table 182.
Table 44 – RegisterNodes Service Result Codes
|
Symbolic Id |
Description |
|
Bad_NothingToDo |
See Table 182 for the description of this result code. |
|
Bad_TooManyOperations |
See Table 182 for the description of this result code. |
|
Bad_NodeIdInvalid |
See Table 183 for the description of this result code. Servers shall completely reject the RegisterNodes request if any of the NodeIds in the nodesToRegister parameter are structurally invalid. |
This Service is used to unregister NodeIds that have been obtained via the RegisterNodes service.
UnregisterNodes does not validate the NodeIds from the request. Servers shall simply unregister NodeIds that are known as registered NodeIds. Any NodeIds that are in the list, but are not registered NodeIds are simply ignored.
Table 50 defines the parameters for the Service.
Table 45 – UnregisterNodes Service Parameters
|
Name |
Type |
Description |
|
Request |
|
|
|
requestHeader |
Request Header |
Common request parameters (see 7.33 for RequestHeader definition). |
|
nodesToUnregister [] |
NodeId |
A list of NodeIds that have been obtained via the RegisterNodes service. |
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|
|
|
|
Response |
|
|
|
responseHeader |
Response Header |
Common response parameters (see 7.34 for ResponseHeader definition). |
Table 51 defines the Service results specific to this Service. Common StatusCodes are defined in Table 182.
Table 46 – UnregisterNodes Service Result Codes
|
Symbolic Id |
Description |
|
Bad_NothingToDo |
See Table 182 for the description of this result code. |
|
Bad_TooManyOperations |
See Table 182 for the description of this result code. |