Example: Extending a subject scheme
You 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 upwards
You 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 deliveryTarget
You 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.
