The ISA-95 Equipment Model is an abstract model that describes classes of logical equipment. The physical equipment is defined by physical assets. In the ISA-95 model, a logical device (equipment) usually does not change, but a physical device may change over time. For example a meter is being used, but it requires service, thus it is replaced by an identical meter. The Physical device gets changed, but in the logic of the system the equipment has not changed. The ISA-95 model further defines classes of equipment that define general functionality or features of a logical piece of equipment. These classes of equipment (EquipmentClassType) would be defined by an EquipmentClassType. Instances of these classes of Equipment are referenced by an EquipmentType, which is a definition of a logical piece of equipment. In a running system there would be multiple instances of the EquipmentType. There would also be multiple EquipmentClassTypes. Figure 24 provides an illustration of this concept. It is also acceptable to define subtypes of EquipmentType, where the associated EquipmentClassType never change and multiple instances of the subtype of EquipmentType exist.

Figure 24 - Abstract Equipment Illustration

Figure 23 illustrates the Equipment Information model which consists of Equipment Types and EquipmentClassTypes. The illustration includes the definition of subtypes of EquipmentClassType, an instance of Equipment, and a subtype of EquipmentType. Any subtype of EquipmentType includes additional restrictions on Instance of the subtype such as the instance can never remove an associated EquipmentClassType.

Figure 25 Equipment Information Model

The role based equipment model contains information about specific equipment, equipment classes, equipment capability tests, and maintenance information associated with equipment. It can also contain information about related Physical Assets. The information about the related Physical Asset is represented as asset assignment information

The asset assignment information would be part of the Equipment model as well as part of the Physical Asset model. The asset assignment information could be time series data and is accessed by standard Attribute Services as defined in OPC 10000-4.

The asset assignment information is represented as DataVariable that is part of the Equipment or Physical Asset. The DataType of the asset assignment VariableType is a structure that represents elements of the asset assignment information. This standard only defines basic information regarding the asset assignment. Third parties may create a subtype of this VariableType to represent third party specific information of an asset assignment. (See Figure 26)

Figure 26 - Asset Assignment Information

This structure contains elements that record the asset assignment.

Table 54 – ISA95AssetAssignmentDataType Structure

Name	Type	Description
ISA95AssignemtDataType	Structure	Information that describes the asset assignment record.
Id	NodeId	Identification that records the asset assignment.
AssignmentDescription	LocalizedText	Additional information or description about the assignment.
StartTime	DateTime	Starting time of the asset assignment.
EndTime	DateTime	Ending time of the asset assignment.

Its representation in the AddressSpace is defined in Table 55.

Table 55 – ISA95AssetAssignmentDataType Definition

Attributes	Value
BrowseName	ISA95AssetAssignmentDataType

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.

The EquipmentCapabilityTestResultType is a concrete VariableType that can be used directly. It is a subtype of ISA95TestResultType VariableType defined in 7.5.4.

This VariableType indicates the results from an Equipment test.

Table 57 – EquipmentCapabilityTestResultType definition

Attribute	Value
BrowseName	EquipmentCapabilityTestResultType
IsAbstract	False
ValueRank	0 (OneOrMoreDimensions)
DataType	Structure
Historizing	True
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the ISA95TestResultType defined in 7.5.4.

This variable type according to ISA-95 shall have prior and or multiple results available depending on the vendor specific model. To accommodate this requirement, vendors will be required to support historical storage of instances of EquipmentCapabilityTestResultType

The EquipmentClassPropertyType is a concrete VariableType that can be used directly. It is a subtype of ISA95ClassPropertyType defined in 7.5.4.

This VariableType indicates ISA95ClassProperties for an EquipmentClassType. Variables of this VariableType may be associated to an instance of an EquipmentCapabilityTestSpecificationType defined in 8.1.3.1.

Table 58 – EquipmentClassPropertyType definition

Attribute	Value
BrowseName	EquipmentClassPropertyType
IsAbstract	False
ValueRank	0 (OneOrMoreDimensions)
DataType	BaseDataType
References		NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the ISA95ClasspropertyType defined in 7.5.2.
HasISA95ClassProperty		Variable	<PropertyName>		EquipmentClassPropertyType	OptionalPlaceholder
TestedByEquipmentTest		Object	<TestSpecification>		EquipmentCapabilityTestSpecificationType	OptionalPlaceholder

<PropertyName> is a placeholder for possible nested instances of EquipmentClassPropertyType. These properties can have any name but shall be referenced using the HasISA95ClassProperty reference and shall be of type EquipmentClassPropertyType or a subtype of it

<TestSpecification> is a placeholder for any test specification that this EquipmentClassPropertyType is tested by. These test specifications can have any name but shall be referenced using the TestedByEquipmentTest Reference and shall be of type EquipmentCapabilityTestSpecificationType or a subtype of it.

The EquipmentPropertyType is a concrete VariableType that can be used directly. It is a subtype of ISA95PropertyType defined in 7.5.3.

This VariableType indicates ISA95Properties of a role based equipment. An instance of an EquipmentPropertyType may be related to instances of EquipmentCapabilityTestSpecificationType defined in 8.1.3.1 and may be tested by the execution of the equipment test specification with results exchanged in an equipment test result.

Table 59 – EquipmentPropertyType definition

Attribute	Value
BrowseName	EquipmentPropertyType
IsAbstract	False
ValueRank	0 (OneOrMoreDimensions)
DataType	BaseDataType
References	NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the ISA95PropertyType defined in 7.5.3.
HasTestResult	Variable	<TestResult>	BaseDataType	EquipmentCapabilityTestResultType	OptionalPlaceholder
HasISA95Property	Variable	<PropertyName>		EquipmentPropertyType	OptionalPlaceholder
TestedByEquipmentTest	Object	<TestSpecification>		EquipmentCapabilityTestSpecificationType	OptionalPlaceholder

<TestResult> is the optional results associated with an EquipmentCapabilityTestSpecificationType. These test results can have any name but shall be referenced using the HasTestResult Reference and shall be of type EquipmentCapabilityTestResultType or a subtype of it. In addition each <TestResult> shall have a ResultsForSpecification Reference to the instance of EquipmentCapabilityTestSpecificationType that it is associated with. It is recommended that the names assigned to the instance of the EquipmentCapabilityTestSpecificationType object and the <TestResult> variable follow some naming convention, to allow operators to more easily match test results to the test specification that they are for.

<PropertyName> is a placeholder for possible additional nested instances of EquipmentPropertyTypes. These properties can have any name but shall be referenced using the HasISA95Property reference and shall be of type EquipmentPropertyType or a subtype of it

<TestSpecification> is a placeholder for any capability test specification that an instance of this EquipmentPropertyType conforms to. These test specifications can have any name but shall be referenced using the TestedByEquipmentTest Reference and shall be of type EquipmentCapabilityTestSpecificationType or a subtype of it

The EquipmentCapabilityTestSpecificationType is a concrete ObjectType that can be used directly. It is a subtype of ISA95TestSpecificationType defined in 7.6.4.

This ObjectType indicates an equipment capability test. An equipment capability test may be associated with an EquipmentClassType and an instance of an EquipmentClassPropertyType, an instance of EquipmentType or an instance of EquipmentPropertyType. This is typically used where a test is required to ensure that the equipment has the necessary capability and capacity. An instance of an EquipmentCapabilityTestSpecificationType may be associated with more than one EquipmentClassType and also to more than one instance of an EquipmentType and also to more than one subtype of an EquipmentType.

Table 60 - EquipmentCapabilityTestSpecificationType

Attribute		Value
BrowseName		EquipmentCapabilityTestSpecificationType
IsAbstract		False
References	NodeClass		BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the ISA95TestSpecificationType defined in 7.6.4.

The EquipmentClassType is an abstract ObjectType; it is expected to be subtyped. It is a subtype of ISA95ClassType defined in 7.6.2.

This ObjectType indicates a grouping of equipment with similar characteristics for a definite purpose such as manufacturing operations definition, scheduling, capability and performance. The EquipmentClassType may be associated to objects of an EquipmentCapabilityTestSpecificationType. It is expected that subtypes of the EquipmentClassType will be created that represent a particular class of equipment. These subtypes will have their own set of instance of EquipmentClassPropertyType and EquipmentCapabilityTestSpecificationType.

Table 61 - EquipmentClassType definition

Attribute	Value
BrowseName	EquipmentClassType
IsAbstract	False
References			NodeClass	BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the ISA95ClassType defined in 7.6.2.
HasISA95Class Property			Variable	<PropertyName>	BaseDataType	EquipmentClassPropertyType	OptionalPlaceholder
TestedByEquipmentTest			Object	<TestSpecification>		EquipmentCapabilityTestSpecificationType	OptionalPlaceholder
HasISA95Attribute			Variable	EquipmentLevel	ISA95EquipmentElementLevelEnum	PropertyType	Optional

<PropertyName> is a placeholder for possible additional nested instances of EquipmentClassPropertyType. These properties can have any name but shall be referenced using the HasISA95ClassProperty reference and shall be of type EquipmentClassPropertyType or a subtype of it

<TestSpecification> is a placeholder for any capability test specification that this EquipmentClassType conforms to. These capability test specifications can have any name but shall be referenced using the TestedByEquipmentTest Reference and shall be of type EquipmentCapabilityTestSpecificationType or a subtype of it

EquipmentLevel is an identification of the level in the role based equipment hierarchy.

The EquipmentType is a concrete ObjectType that can be used directly. It is a subtype of ISA95ObjectType defined in 6.7.2.

This ObjectType defines a piece of equipment. Equipment may be tested by the execution of one or more tests defined by EquipmentCapabilityTestSpecificationType. Individual instance of this EquipmentType would have one or more reference(s) to EquipmentClassType(s) that the instance of the EquipmentType is defined by. A subtype of EquipmentType may also be defined for a fixed set of referenced EquipmentClassTypes. By definition of the ISA-95 model, when an Equipment instance or a sub type of EquipmentType references an EquipmentClassType, the addition of said reference results in the addition of all instances of EquipmentClassPropertyType defined for the referenced EquipmentClassType to the Equipment instance (or EquipmentType subtype) as instances of EquipmentPropertyType. These instances of EquipmentPropertyType will have all the same Attributes and Properties as the corresponding EquipmentClassPropertyType instance. This includes the same value for the BrowseName, DisplayName, Description and any other properties.

This ObjectType may be further subtyped. The subtypes create some additional restrictions. Any EquipmentClassType references that are added to a subtype of an EquipmentType cannot be removed from an instance of the subtype. If the EquipmentType subtype is updated then all instance of the EquipmentType subtype must also be updated. For example if an additional EquipmentClassType is added to the EquipmentType subtype that that EquipmentClassType must be added to all instances of the EquipmentType subtype. This allows for creating a single EquipmentType that is used for multiple EquipmentType instances.

Equipment may be made of other equipment.

Table 62 – EquipmentType definition

Attribute		Value
BrowseName		EquipmentType
IsAbstract		False
References	NodeClass		BrowseName	DataType	TypeDefinition	ModellingRule
Subtype of the ISA95ObjectType defined in 7.6.3.
HasISA95Property	Variable		<PropertyName>	BaseDataType	EquipmentPropertyType	OptionalPlaceholder
DefinedByEquipmentClass	Object		<EquipmentClass>		EquipmentClassType	OptionalPlaceholder
TestedByEquipmentTest	Object		<TestSpecification>		EquipmentCapabilityTestSpecificationType	OptionalPlaceholder
MadeUpOfEquipment	Object		<Equipment>		EquipmentType	OptionalPlaceholder
HasISA95Attribute	Variable		EquipmentLevel	ISA95EquipmentElementLevelEnum	PropertyType	Optional
ImplementedBy	Object		PhysicalAsset		PhysicalAssetType	Optional
HasComponent	Variable		AssetAssignment	structure	ISA95AssetAssignmentType	Optional

<PropertyName> is a placeholder for possible additional instances of EquipmentPropertyType. These properties can have any name but shall be referenced using the HasISA95Property reference and shall be of type EquipmentPropertyType or a subtype of it

<EquipmentClass> is a placeholder for possible related EquipmentClassTypes These EquipmentClassTypes can have any name but shall be referenced using the DefinedByEquipmentClass reference and shall be an EquipmentClassType or a subtype of it

<TestSpecification> is a placeholder for any capability test specification that instances of this EquipmentType conform to. These test specifications can have any name but shall be referenced using the TestedByEquipmentTest Reference and shall be of type EquipmentCapabilityTestSpecificationType or a subtype of it

<Equipment> is a placeholder for sub instances of EquipmentType. These instances of EquipmentType can have any name but shall be referenced using the MadeUpOfEquipment reference and shall be an instance of EquipmentType or a subtype of it

EquipmentLevel is an identification of the level in the role based equipment hierarchy.

PhysicalAsset is an instance of a PhysicalAssetType that is assigned to this instance of an EquipmentType.

AssetAssignment – Is used to track the history of the physical assets assigned to this logical equipment.