Data that describes structure and semantics for data (business, physical, and so on), information (people, processes, places, and so on), and knowledge (business rules, unstructured information, and so on).
Examples include: for data, the definition of a source to target transformation that is used to generate and populate the data warehouse; for information, definitions of tables, columns, and associations that are stored inside a relational modeling tool; for a business rule, discount by 10 percent after selling 1,000 items.