Lecture02 - What you should have learned after this lecture...

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Unformatted text preview: What you should have learned after this lecture ... the main concepts of the so-called three-level model what data independence means and why it is important understand roughly the software architecture of a database management system 1.5 Data Abstraction: The Three-Level Model physical schema conceptual schema external schema 1 transformation rules conceptual/physical schema database external schema n ... transformation rules 1 external/conceptual schema transformation rules n external/conceptual schema external levels (views of separate user groups) conceptual level (general logical view) physical level (storage view) DBMS operating system DBS has several abstraction lev- els external/view levels describe the part of the DB, which is rel- evant for the user conceptual/logical level gives information about exist- ing data and relationships in the DB physical/internal level describes how data are physi- cally stored Database schema and state a schema describes the struc- ture/the design of a DB a state describes a concrete instance of a DB 1.61....
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Lecture02 - What you should have learned after this lecture...

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