Inmon advocates using a central data repository design to hold all the data in a structured normalized manner.
Access to the data is typically through data marts, which are a subset of the data warehouse repository in an optimized for use structure. These structures can be third normal form (3NF), star, or snowflake designs. Many IT initiatives begin with a pure top-down approach.
Kimball advocates data mart models built on a bus architecture, which is simply conformed dimensions. These data marts are star designs but can snowflake out, although this is not desired. There is no central repository because all dimensions are conformed, meaning that they are reusable in different data marts as needed. Most business requirement–focused projects begin with a bottom-up approach.