External schema

An External schema (also called view schema) is created with the intention to deal with how the end users of a system "view" the data. Thus "external" is differentiated here from the conceptual and internal schemas. This is inline with the Three schema approach which is also applied in the Three tier architecture and a proven and widespread way of designing systems. In the following diagram depicting a multitier-architecture. The external schema would be adapted to the Clients, the conceptual schema to the business/application logic and the internal schema to the datasources which might be databases.