The term external semantics describes a variety of technques that can be used to apply semantics to documents or objects that do not natively have them. Some documents have some level of semantics explicitly built into them, for example, schema.org markup can be used in a web page. When there is no explicit semantics, it may be possible to create external semantics either manually, by describing regions, or automatically using techniques such as data detectors.
Used in Chap. 17: pages 250, 259