Table 60 describes the required content of the RefMeta element and its Meta child elements describing a Data Object.
Table 60 – RefMeta child elements
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<RefMeta Prefix=“opc http://opcfoundation.org/PNGSDGM/”> |
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Child element |
Property attribute of child element |
Required Content attribute of child element |
Mandatory/Optional |
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<Meta> |
opc:Name |
Brief denomination of the Data Object, e.g. “Discharge Temperature”, “Ambient Pressure” and the like. |
M |
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<Meta> |
opc:EngineeringUnit |
Mapped UNECE code of the 0:EUInformation data type (see [OPC 10000-8], 5.6.3) representing the engineering unit of this Data Object. |
O |
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<Meta> |
opc:EURange |
Upper and lower engineering unit boundary of the data value in the format “<upper>;<lower>”. Represent with 0:Range type Property as part of an AnalogUnitRangeType Variable representing the Data Object. For numeric data only. Specify only in conjunction with “opc:EngineeringUnit”. |
O |
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<Meta> |
opc:FunctionGroupName |
Path name for the OPC UA 2:FunctionalGroupType container object which shall be created by an OPC UA Server for the object representing the Data Object. The path names provided for the Data Objects can define a folder hierarchy using file system path syntax: <parent folder/subfolder 1/../subfolder n>. The RefMeta element of one Data Object may contain this Meta element more than once. If so, the representing OPC UA Variable becomes a component of different container Objects. |
O |
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<Meta> |
opc:DataMapping |
Desired OPC UA representation for the Data Object: “Variable” or “Property”. If no “Meta” element with this attribute is provided, the representation defaults to “Variable”. |
O |
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<Meta> |
opc:Offset |
Calculation factor to be applied by an OPC UA Server to obtain the actual display value in the Information Model. To be used in conjunction with the “opc:Gradient” Meta element, see below. |
O |
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<Meta> |
opc:Gradient |
Calculation factor to be applied by an OPC UA Server to obtain the actual display value in the Information Model. To be used in conjunction with the “opc:Offset” Meta element, see above. Regardless of the referenced Data Object’s data type specified by the parent “Ref” element, if “opc:Offset” and “opc:Gradient” Meta elements are provided, the DataType in the Information Model shall always be 0:Float or 0:Double. The display value shall always be calculated asValue = (value read from Device * Gradient) + Offset. |
O |
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<Meta> |
opc:DestinationDataType |
Name of the OPC UA base data type to be used as DataType for the Variable or Property which represents the data value in the Information Model, e.g. “0:UInt16”. Overrides the mapping defined in Table 58. |
O |
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As shown in Figure 15, the “ParameterRecordDataItem” elements may contain an optional “RecordMeta” element. The schema defined for the “RecordMeta” element is the same as the schema of the “RefMeta” elements (see Figure 20 also). Table 61 shows the required content of the optional RecordMeta element.