The ISA95AssetAssignmentType is a concrete VariableType that can be used directly. It is a subtype of BaseDataVariableType defined in OPC 10000-5.

This VariableType is used to track the asset assignment, It is usually includes history. The Variables associated with VariableType provide the asset assignment information. The structure of asset assignment information can be extended. Therefore, third party may design particular structure for the asset assignment information. This standard defines the minimum information elements for the asset assignment.

Table 56 - ISA95AssetAssignmentType definition

Attribute		Value
BrowseName		ISA95AssetAssignmentType
IsAbstract		False
ValueRank		0 (OneOrMoreDimensions)
DataType		Structure
Historizing		True
References	NodeClass		BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the BaseDataVariableType defined in OPC 10000-5
HasISA95Attribute	Variable		Id	NodeId	PropertyType	Mandatory
HasISA95Attribute	Variable		AssignmentDescription	LocalizedText	PropertyType	Mandatory
HasISA95Attribute	Variable		StartTime	DateTime	PropertyType	Mandatory
HasISA95Attribute	Variable		StopTime	DateTime	PropertyType	Mandatory

This variable type according to ISA-95 shall maintain prior and/or support multiple results depending on the vendor specific information model. To accommodate this requirement, vendors will be required to support historical storage of the value for instances of ISA95AssetAssignmentType.

From history a user can determine all of the physical assets that were used to represent this logical piece of equipment. Also the history of all logical equipment a particular physical asset was assigned to can be reviewed, when this variable is used on a physical asset.

Id is an identifier of the asset assignment information. This id is the NodeId of the instance of PhysicalAssetType that is currently assigned to this piece of equipment (if this variable is part of an Equipment object). This VariableType is also used for PhysicalAssetType objects, in which case this id would be the NodeId of the instance of the EquipmentType that the physical asset is assigned to.

AssignmentDescription is an additional information or description of the assignment.

StartTime is the time at which the asset assignment was made.

StopTime is the time at which the asset assignment was change / ended.

This standard defines ISA95AssetAssignmentDataType as the default DataType. Third parties may define their own structure that contains additional elements, but it must still contain all the elements defined in the ISA95AssetAssignmentDataType. It is also recommended that any new items that are added to the new ISA95AssetAssignmentDataType also be added to the new subtype of the ISA95AssetAssignmentType variable type.