Bill Inmon’s paradigm: Data warehouse is one part of the overall business intelligence system. An enterprise has one data warehouse, and data marts source their information from the data warehouse. In the data warehouse, information is stored in 3rd normal form.
Inmon’s approach, also called top-down, is to have “one version of the truth“, a great entity that contains all the information for the entire enterprise in one place, an entity called the data warehouse. According to him, the data warehouse should operate in a relational format and store all of the organization’s atomized data. Once the data warehouse is fully designed and put in place, only then can small data marts be added for different departments to query data from the central data warehouse and store it in various dimensions.
Ralph Kimball’s paradigm: Data warehouse is the conglomerate of all data marts within the enterprise. Information is always stored in the dimensional model.
Kimball suggests that an organization should first build small data marts for each department. The data marts should contain facts and dimensions relevant to the business area and store them in a star or snowflake schema. As far as Kimball is concerned, the data warehouse is essentially a union of all the data marts. Accordingly, his version is called bottom-up.