1. A machine-implemented method, comprising: acquiring schemas for applications that store data in a data warehouse; applying rules to detect a plurality of data types defined in the schemas that match in response to patterns defined in the rules, wherein each data type is defined in a different one of the schemas; and generating a master schema for the data types that merges each definition for each data type from each data type's corresponding schema into a single master definition that defines the data types as a whole within the master schema.