A data warehouse stores minimally processed data. A data warehouse includes raw (or minimally processed) data, metadata, and summary data. William H. Inmon originally defined a data warehouse as "a subject-oriented, integrated, time-variant, and nonvolatile collection of data in support of management's decision-making process." When used informally, data warehousing can describe any process of storing data in useful formats for later processing, up to and including formal data modeling and database storage (although warehousing typically indicates a less structured approach). Subsets with specific foci are called **data marts**.