Introduction |
This topic contains the following sections:
The Information Model describes standardised nodes of a server’s Address Space. These nodes are standardised types as well as standardised instances used for diagnostics or as entry points to server specific nodes. Thus, the Information Model defines the Address Space of an empty OPC Unified Architecture server. However, it is not expected that all servers will provide all of these nodes.
NodeId and BrowseNameThe value of the NodeId attribute of all nodes described in this part are only symbolic names. Mappings defines the actual NodeId values.
The symbolic name of each node defined in this document is its BrowseName, or, when it is part of another node, the BrowseName of the other node, a ".", and the BrowseName of itself. In this case "part of" means that the whole has a HasProperty or HasComponent reference to its part. Since all nodes not being part of another node have a unique name in this document, the symbolic name is unique.
For example, the ServerType has the symbolic name “ServerType”. One of its instance declarations would be identified as “ServerType.ServerCapabilities”. Since this object is complex, another instance declaration of the ServerType is “ServerType.ServerCapabilities.MinSupportedSampleRate”. The Server object is based on the ServerType and has the symbolic name “Server”. Therefore, the instance based on the instance declaration described above has the symbolic name “Server.ServerCapabilities.MinSupportedSampleRate”.
The namespace index for all NodeId attribute values defined in this section is 0. The namespace for this namespace index is specified in NodeId
 Note |
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The OPC Unified Architecture specification does not only define concrete nodes, but also requires that some nodes have to be instantiated by the server in the exposed Address Space, for example one for each Session running on the server. The values of the NodeId attribute of those nodes are server-specific, including the Namespace. But the namespace index of those nodes cannot be equal 0, because they are not defined by the OPC Foundation but generated by the server. |
The text part of the BrowseName for all nodes defined in this part is specified in the sections defining the nodes. The namespace index for all BrowseName values defined in this section is equal 0.
Common AttributesThis section contains the following subsections:
General
For all nodes specified in this part, the attributes shall be set as specified in the table.
Attribute | Type | Value |
|---|---|---|
The DisplayName attribute is a LocalizedText. Each server shall provide the DisplayName attribute identical to the BrowseName of the node for the LocaleId “en”. Whether the server provides translated names for other LocaleId values is vendor specific. | ||
Description | Optionally a vendor specific description is provided. | |
NodeClass | Shall reflect the node class of the node. | |
NodeId | The NodeId attribute is described by browse names and defined in Mappings | |
WriteMask | Optionally the WriteMask attribute can be provided. If the WriteMask attribute is provided, it shall set all attributes to not writeable that are not said to be vendor-specific. For example, the Description attribute may be set to writeable since a server may provide a server-specific description for the node. The NodeId attribute shall not be writeable, because it is defined for each node in the OPC Unified Architecture specification. | |
UserWriteMask | Optionally the UserWriteMask attribute can be provided. The same rules as for the WriteMask attribute apply. |
Objects
For all objects specified in this section, the following attributes shall be set as specified in the table.
Attribute | Type | Value |
|---|---|---|
EventNotifier | Whether the node can be used to subscribe to events or not is vendor specific (see also Summary of Attributes). |
Variables
For all variables specified in this part, the following attributes shall be set as specified in the table.
Attribute | Type | Value |
|---|---|---|
MinimumSamplingInterval | Optionally, a vendor-specific minimum sampling interval is provided. | |
AccessLevel | The access level for variables used for type definitions is vendor-specific, for all other variables defined in this part, the access level shall allow a current read; other settings are vendor specific. | |
UserAccessLevel | The value for the UserAccessLevel attribute is vendor-specific. It is assumed that all variables can be accessed by at least one user. See also Summary of Attributes. | |
Value | Defined by the DataType attribute | For variables used as instance declarations, the value is vendor-specific; otherwise it shall represent the value described in the text. The most recent value of the Variable that the server has. Its data type is defined by the DataType attribute. It is the only attribute that does not have a data type associated with it. |
ArrayDimensions | If the ValueRank does not identify an array of a specific dimension (i.e. ValueRank <= 0) the ArrayDimensions attribute can either be set to null or the attribute is missing. This behaviour is vendor-specific. If the ValueRank attribute specifies an array of a specific dimension (i.e. ValueRank > 0) then the ArrayDimensions attribute shall be specified in the table defining the Variable. |
Variable Types
For all VariableType nodes specified in this section, the attributes shall be set as specified in the table.
Attribute | Type | Value |
|---|---|---|
ArrayDimensions | If the ValueRank does not identify an array of a specific dimension (i.e. ValueRank <= 0) the ArrayDimensions attribute can either be set to null or the attribute is missing. This behaviour is vendor-specific. If the ValueRank attribute specifies an array of a specific dimension (i.e. ValueRank > 0) then the ArrayDimensions attribute shall be specified in the table defining the Variable. |
See Also