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Transcript
Three-Schema Architecture

Mappings among schema levels are needed to
transform requests and data.


Programs refer to an external schema, and are
mapped by the DBMS to the internal schema for
execution.
Data extracted from the internal DBMS level is
reformatted to match the user’s external view (e.g.
formatting the results of an SQL query for display
in a Web page)
Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe
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