tailieunhanh - Lecture Database - Chapter 4: Enhanced Entity-Relationship and UML modeling

EER Model includes all modeling concepts of basic ER and additional concepts: subclasses/superclasses (lớp con/lớp cha), specialization (chuyên biệt)/generalization (tổng quát); categories, attribute inheritance (phân cấp). It is used to model applications more completely and accurately if needed. It includes some object-oriented concepts, such as inheritance. | Chapter 4 Enhanced Entity-Relationship and UML Modeling Enhanced-ER EER Model Concepts EER Model Includes all modeling concepts of basic ER and Additional concepts - Subclasses superclasses. lớp con lớp cha - Specialization chuyên biệt generalization tổng quát . - Categories attribute inheritance phân cấp It is used to model applications more completely and accurately if needed It includes some object-oriented concepts such as inheritance Subclasses and Superclasses An entity type may have additional meaningful subgroupings of its entities Example Employee may be further grouped into Secretary Engineer Manager Technician . Each of these groupings is a subset of EMPLOYEE entities - Each is called a subclass of EMPLOYEE - EMPLOYEE is the superclass for each of these subclasses These are called superclass subclass relationships. Example - Employee secretary. - Employee .