In order to provide hierarchical location information, this specification defines two mechanisms, that can be used individual or in combination.

• The hierarchical location Property provides a simple string providing the hierarchical location of an asset. The structure inside the string may expose several levels. How this is exposed, what delimiters are used, etc. is vendor-specific. Examples of such strings are “FactoryA/BuildingC/Floor1” or “Area1-ProcessCell17-Unit4”
• The hierarchical location Objects provide a browsable structure of the hierarchy and simplifies access like getting all assets of one hierarchical location.

In Figure 11, an example is given exposing the hierarchical location by Properties.

Figure 11 – Example of Hierarchical Location using Properties

In Figure 12, an example is given exposing the hierarchical location by Objects. The standardized 0:Locations Object (see 13.3.3.2) is used as entry point.

Figure 12 – Example of Hierarchical Location using Objects

In Figure 13, an example is given combining both approaches.

Figure 13 – Example of Hierarchical Location using Properties and Objects

As shown in the figure, X:Asset0 is referenced by the X:Unit1 of X:Cell4 of X:Area1. The Property HierarchicalLocation provides the same information. As the format of the string is not further defined, it is vendor-specific how to keep both information sources in sync, especially when the Property is writable. Servers may reject Values not represented by Objects or may extend the Locations hierarchy.

Each asset exposing the hierarchical location as Property has a Property with the BrowseName “HierarchicalLocation” (defined in the Namespace of this specification) and the DataType String or a subtype. The structure of the String (e.g. delimiters for different hierarchies) is not further defined in this specification.

Servers may set the HierarchicalLocation Property to be writable to allow Clients to set the hierarchical location of an asset. Servers may provide the HierarchicalLocation with a Null Value or empty string in case the HierarchicalLocation is unknown to the Server and not set by any Client.

In order to expose the hierarchical location as Objects, there is a standardized entry point HierarchicalLocations (see 13.3.3.2). Each Object referenced from the HierarchicalLocations Object with an Organizes Reference or a subtype represents the highest level of a location hierarchy. The ObjectType for those Objects is not further defined, it can be of any ObjectType. Companion specifications might further refine the ObjectType. These Objects may reference other Objects with hierarchical References, exposing deeper level of the hierarchy. The ReferenceType is not further restricted, it is recommended to use the HasComponent ReferenceType. The hierarchy spanned should not contain loops, however, Clients shall not rely on this.

The HierarchicalContains ReferenceType (see 13.3.3.3) is used to relate the contained assets in the corresponding hierarchical location and is excluded from spanning the location hierarchy.

Since the Objects under the HierarchicalLocations Object span a location hierarchy, each asset is only referenced from the deepest level in the hierarchy it belongs to. Implicitly, those assets are also contained from the higher levels in the hierarchy.

The HierarchicalLocations Object is formally defined in Table 50.

Table 50 – HierarchicalLocations definition

Attribute	Value
BrowseName	HierarchicalLocations
Description	Entry point for objects representing the root of a location hierarchy
References	NodeClass	BrowseName	DataType	TypeDefinition
OrganizedBy by the 0:Locations Object defined in OPC 10000-5
0:HasTypeDefinition	ObjectType	0:FolderType
Conformance Units
AMB Hierarchical Location Objects

Objects referenced with an Organizes Reference or a subtype are considered to be the root of a location hierarchy. The HierarchicalLocations Object is the entry point to those root Objects.

HierarchicalContains is a concrete ReferenceType and can be used directly. It is a subtype of Contains.

The semantic of this ReferenceType is to link an Object representing part in a hierarchical location to Objects (like assets) located in that hierarchical location.

The SourceNode of References of this type shall be an Object representing a location. This Object should be part of a hierarchy referenced by the HierarchicalLocations Object, directly or indirectly.

The TargetNode of this ReferenceType shall be an Object contained in the location of the SourceNode.

References of this ReferenceType shall always be exposed bidirectional, i.e. navigating from the location and to the location shall be supported.

The HierarchicalContains is formally defined in Table 51.

Table 51 – HierarchicalContains definition

Attributes	Value
BrowseName	HierarchicalContains
InverseName	HierarchicalLocatedIn
Symmetric	False
IsAbstract	False
Description	Links an Object representing part in a hierarchical location to Objects (like assets) located in that hierarchical location
References	NodeClass	BrowseName	Comment
Subtype of Contains
Conformance Units
AMB Hierarchical Location Objects