Topics is an instance of AliasNameCategoryType. Topics shall restrict instances of AliasNameType to only have AliasFor References that point to PublishedDataSetType (or subtypes) instances (PublishedDataSetType is defined in OPC 10000-14). The Topics Node instance is formally defined in Table 11.

Table 11 - Topics definition

Attribute	Value
BrowseName	Topics
References	NodeClass	BrowseName	DataType	TypeDefinition
OrganizedBy by the Aliases defined in 9.2
HasTypeDefinition	ObjectType	AliasNameCategoryType	Defined in 6.3
ConformanceUnits
AliasName Category Topics

It can contain additional AliasNameCategoryType Objects, which could be used to create a hierarchy or other structure. A single instance of AliasNameType can exist in more than one location in the hierarchy, but all instances in the Topics hierarchy must point to an instance of a PublishedDataSetType.