TAILIEUCHUNG - Lecture Fundamentals of database systems: Chapter 4 - Emasri, Navathe

In this chapter, we describing features that have been proposed for semantic data models, and show how the ER model can be enhanced to include these concepts, leading to the Enhanced ER (EER) model. | EER stands for Enhanced ER or Extended ER EER Model Concepts Includes all modeling concepts of basic ER Additional concepts subclasses superclasses specialization generalization categories UNION types attribute and relationship inheritance These are fundamental to conceptual modeling The additional EER concepts are used to model applications more completely and more accurately EER includes some object-oriented concepts such as inheritance An entity type may have additional meaningful subgroupings of its entities Example EMPLOYEE may be further grouped into SECRETARY ENGINEER TECHNICIAN . Based on the employee s Job MANAGER employees who are managers SALARIED_EMPLOYEE HoUrLY_EMPLOYEE Based on the employee s method of pay EER diagrams extend ER diagrams to represent these additional subgroupings called subclasses or subtypes Copyright 2007 Ramez Elmasri and Shamkant B. Navathe Slide 4-3 Copyright 2007 Ramez Elmasri and Shamkant B. Navathe lide 4-4 Copyright 2007 RamezElmasri and Shamkant B. Navathe lide 4- Each of these subgroupings 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 EMPLOYEE SECRETARY EMPLOYEE TECHNICIAN EMPLOYEE MANAGER Copyright 2007 RamezElmasri and Shamkant B. Navathe lide 4- 1 These are also called IS-A relationships . SECRETARY IS-A EMPLOYEE TECHNICIAN IS-A EMPLOYEE . Note An entity that is member of a subclass represents the same real-world entity as some member of the superclass The subclass member is the same entity in a distinct specific role An entity cannot exist in the database merely by being a member of a subclass it must also be a member of the superclass A member of the superclass can be optionally included as a member of any number of its subclasses Examples A salaried employee who is also an engineer belongs to the two subclasses ENGINEER and SALARIED_EMPLOYEE A salaried employee who is also an engineering

• Cơ sở dữ liệu
• Database systems
• Fundamentals of database systems
• Enhanced Entity Relationship modeling
• Enhanced ER model
• EER model concepts
• EER Diagrams
• Lecture Database Systems
• Database systems concepts
• Database systems architecture
• Database languages
• Data management systems framework
• Introduction to Database Systems
• Database system concepts
• Entity Relationship model
• Database security
• Distributed database systems
• Principles of distributed database systems
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• Parallel database systems
• Load balancing
• Database architecture
• Database approach
• Database management systems
• Lecture Database management systems
• File based system
• Characteristics of the database
• Data dictionary
• Database integration
• Schema matching
• The relational data model
• Database design
• Database programming techniques
• Relational database constraints
• Database System
• Relational databases
• Relational database design algorithms
• Relational database systems
• Computer networks
• Practical Database Design
• Physical Database Design in Relational Databases
• An Overview of Database Tuning in Relational Systems
• Physical Database Design Decisions
• Data models
• Hierarchical model
• Designing a set of relations
• Relational decompositions
• Relational database schema
• Database users
• Database applications
• Typical DBMS functionality
• Databases and database users
• Relational calculus
• Physical database design
• Concurrency control techniques
• Database recovery techniques
• Distributed databases
• Multivalued dependencies
• Fundamentals of database management systems
• Logical database design
• Object oriented database management
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• Design problem
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• Database development
• Database environments
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• Object database
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• Operating systems
• Attribute alias
• Lecture Database system concepts
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• Relational database design