Ralph Kimball - bottom-up design: approach data marts are first created to provide reporting and analytical capabilities for specific business processes.
Data marts - contain, primarily, dimensions and facts.
Facts - either contain atomic (detailed) data, and, if necessary, summarized data.
Single data mart often models a specific business area (unit) i.e. "Sales," "Production."
Integration of data marts is managed through implementation is called: "data warehouse bus architecture."
Data Warehouse bus architecture: is an implementation of "the bus," a collection of conformed dimensions and conformed facts, which are dimensions that are shared (in a specific way) between facts in two or more data marts.