Examples of subject scheme maps This section contains examples and scenarios that illustrate the use of subject scheme maps. Example: How hierarchies defined in a subject scheme map affect filteringThis scenario demonstrates how a processor evaluates attribute values when it performs conditional processing for an attribute that is bound to a set of controlled values.Example: Extending a subject schemeYou can extend a subject scheme by creating another subject scheme map and referencing the original map using a <schemeref> element. This enables information architects to add new relationships to existing subjects and extend enumerations of controlled values.Example: Extending a subject scheme upwardsYou can broaden the scope of a subject category by creating a new subject scheme map that defines the original subject category as a child of a broader category.Example: Defining values for deliveryTargetYou can use a subject scheme map to define the values for the @deliveryTarget attribute. This filtering attribute, which is new in DITA 1.3, is intended for use with a set of hierarchical, controlled values.Parent topic: Subject scheme maps and their usage