Chapter 3 Building Conceptual and Logical Diagrams

Conceptual Diagram Basics

A Conceptual Data Model (CDM) represents the structure of your database, independent of any software or data storage structure. It describes entities (things of significance to a organization) and their identifiers and other attributes, along with the relationships and inheritances that connect them.

In the following conceptual diagram, the Teacher and Student entities inherit attributes from the Person parent entity. The two child entities are linked with a one-to-many relationship (a teacher has several students but each student has only one main teacher).

In addition:

• a teacher can teach several subjects and a subject can be taught by several teachers (many-to-many).
• a teacher can teach several lessons and a lesson is taught by only one teacher (one-to-many).
• a student attends multiple lessons and a lesson is followed by multiple students (many-to-many).
• a student studies multiple subjects and a subject can be studied by multiple students (many-to-many).

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