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1 © Prentice Hall, 2002 Chapter 4: The Enhanced E-R Model and Business Rules Modern Database Management 6 th Edition Jeffrey A. Hoffer, Mary B. Prescott, Fred R. McFadden
Chapter 4 2 © Prentice Hall, 2002 Supertypes and Subtypes Subtype: Subtype: A subgrouping of the entities in an entity type which has attributes that are distinct from those in other subgroupings Supertype: Supertype: An generic entity type that has a relationship with one or more subtypes Inheritance: Inheritance: – Subtype entities inherit values of all attributes of the supertype – An instance of a subtype is also an instance of the supertype
Chapter 4 3 © Prentice Hall, 2002 Figure 4-1 Basic notation for supertype/subtype relationships
Chapter 4 4 © Prentice Hall, 2002 Figure Employee supertype with three subtypes All employee subtypes will have emp nbr, name, address, and date-hired Each employee subtype will also have its own attributes
Chapter 4 5 © Prentice Hall, 2002 There is always an implicit IS-A relationship between a sub-entity and its super-entity Cardinality of IS-A is always maximum 1-1 and minimum 1-0 (super-entity — sub-entity) Super-entity — Sub-entity Cardinality EMPLOYEE PROGRAMMER IS-A
Chapter 4 6 © Prentice Hall, 2002 Relationships and Subtypes Relationships at the supertype level indicate that all subtypes will participate in the relationship The instances of a subtype may participate in a relationship unique to that subtype. In this situation, the relationship is shown at the subtype level
Chapter 4 7 © Prentice Hall, 2002 Figure Supertype/subtype relationships in a hospital Both outpatients and resident patients are cared for by a responsible physician Only resident patients are assigned to a bed
Chapter 4 8 © Prentice Hall, 2002 Generalization and Specialization BOTTOM-UP Generalization: The process of defining a more general entity type from a set of more specialized entity types. BOTTOM-UP TOP-DOWN Specialization: The process of defining one or more subtypes of the supertype, and forming supertype/subtype relationships. TOP-DOWN
Chapter 4 9 © Prentice Hall, 2002 Figure 4-4 – Example of generalization (a) Three entity types: CAR, TRUCK, and MOTORCYCLE All these types of vehicles have common attributes
Chapter 4 10 © Prentice Hall, 2002 Figure 4-4(b) – Generalization to VEHICLE supertype So we put the shared attributes in a supertype Note: no subtype for motorcycle, since it has no unique attributes
Chapter 4 11 © Prentice Hall, 2002 Figure 4-5 – Example of specialization (a) Entity type PART Only applies to manufactured parts Applies only to purchased parts
Chapter 4 12 © Prentice Hall, 2002 Figure 4-5(b) – Specialization to MANUFACTURED PART and PURCHASED PART Note: multivalued attribute was replaced by a relationship to another entity Created 2 subtypes
Chapter 4 13 © Prentice Hall, 2002 Constraints in Supertype/ Completeness Constraint Completeness Constraints : Whether an instance of a supertype must also be a member of at least one subtype – Total Specialization Rule: Yes (double line) – Partial Specialization Rule: No (single line)
Chapter 4 14 © Prentice Hall, 2002 Figure 4-6 – Examples of completeness constraints (a) Total specialization rule A patient must be either an outpatient or a resident patient
Chapter 4 15 © Prentice Hall, 2002 Figure 4-6(b) – Partial specialization rule A vehicle could be a car, a truck, or neither
Chapter 4 16 © Prentice Hall, 2002 Constraints in Supertype/ Disjointness constraint Disjointness Constraints : Whether an instance of a supertype may simultaneously be a member of two (or more) subtypes. – Disjoint Rule: An instance of the supertype can be only ONE of the subtypes – Overlap Rule: An instance of the supertype could be more than one of the subtypes
Chapter 4 17 © Prentice Hall, 2002 (a) Disjoint rule Figure 4-7 – Examples of disjointness constraints A patient can either be outpatient or resident, but not both
Chapter 4 18 © Prentice Hall, 2002 Figure 4-7(b) Overlap rule A part may be both purchased and manufactured
Chapter 4 19 © Prentice Hall, 2002 Constraints in Supertype/ Subtype Discriminators Subtype Discriminator : An attribute of the supertype whose values determine the target subtype(s) – Disjoint – a simple attribute with alternative values to indicate the possible subtypes – Overlapping – a composite attribute whose subparts pertain to different subtypes. Each subpart contains a boolean value to indicate whether or not the instance belongs to the associated subtype
Chapter 4 20 © Prentice Hall, 2002 Figure 4-8 – Introducing a subtype discriminator ( disjoint rule) A simple attribute with different possible values indicating the subtype
Chapter 4 21 © Prentice Hall, 2002 Figure 4-9 – Subtype discriminator ( overlap rule) A composite attribute with sub-attributes indicating “yes” or “no” to determine whether it is of each subtype
Chapter 4 22 © Prentice Hall, 2002 Figure 4-10 – Example of supertype/subtype hierarchy
Chapter 4 23 © Prentice Hall, 2002 Entity Clusters EER diagrams are difficult to read when there are too many entities and relationships Solution: group entities and relationships into entity clusters Entity cluster: set of one or more entity types and associated relationships grouped into a single abstract entity type
Chapter 4 24 © Prentice Hall, 2002 Figure 4-13(a) – Possible entity clusters for Pine Valley Furniture Related groups of entities could become clusters
Chapter 4 25 © Prentice Hall, 2002 Figure 4-13(b) – EER diagram of PVF entity clusters More readable, isn’t it?
Chapter 4 26 © Prentice Hall, 2002 Business rules Statements that define or constrain some aspect of the business. Constraints can impact: – Structure (definition, domain, relationship) – Behavior (operational constraints) Classification of business rules: – Derivation – rule derived from other knowledge – Structural assertion – rule expressing static structure – Action assertion – rule expressing constraints/control of organizational actions
Chapter 4 27 © Prentice Hall, 2002 Figure 4-16 – Data model segment for class scheduling
Chapter 4 28 © Prentice Hall, 2002 Figure 4-17 – Business Rule 1: For a faculty member to be assigned to teach a section of a course, the faculty member must be qualified to teach the course for which that section is scheduled Action assertion Anchor object Corresponding object R In this case, the action assertion is a R estriction
Chapter 4 29 © Prentice Hall, 2002 Figure 4-18 – Business Rule 2: For a faculty member to be assigned to teach a section of a course, the faculty member must not be assigned to teach a total of more than three course sections Action assertionAnchor object Corresponding object In this case, the action assertion is an ULIM U pper LIM it
Conceptual Design Modeling the rules of organization Modeling the rules of organization Building ER model Building ER model.
© 2005 by Prentice Hall Chapter 9 Structuring System Data Requirements Modern Systems Analysis and Design Fourth Edition Jeffrey A. Hoffer Joey F. George.
©Silberschatz, Korth and Sudarshan2.1Database System Concepts Chapter 2: Entity-Relationship Model Entity Sets Relationship Sets Design Issues Mapping.
Database System Concepts, 5th Ed. ©Silberschatz, Korth and Sudarshan See for conditions on re-usewww.db-book.com Chapter 6: Entity-Relationship.
Chapter 7 Relational Database Design by ER- and EERR-to-Relational Mapping Copyright © 2004 Pearson Education, Inc.
Chapter 2: Entity-Relationship Model Entity Sets Relationship Sets Design Issues Mapping Constraints Keys E-R Diagram Extended E-R Features Design of an.
Entity Relationship (ER) Modeling The ER Model Developing and ER Diagram Extended ER Model Entity Integrity : Selecting Primary Key Chapter 4.
Data, Information & Knowledge Database DBMS Types of Models E-R Model.
©Ian Sommerville 2000 Software Engineering, 6th edition. Chapter 7 Slide 1 Chapter 7 System Models.
9/2/2014 1Yan Huang - ER Chapter 6: ER – Entity Relationship Diagram Major components of ER diagram Major components of ER diagram Practices Practices.
3 Entity Relationship (E-R) Modeling. 3 2 In this lecture, you will learn: What a conceptual model is and what its purpose is The difference between internal.
Conceptual / semantic modelling 1. 2 Overview design; conceptual design; ER model concepts; semantic aspects; problems; Enhanced ER (EER) modelling; transforming.
ER-to-Relational Mapping 1. Relational Database Design : ER- Mapping.
Entity/Relationship Modelling. Topics To Be Covered In This Lecture Entity/Relationship models Entities and Attributes Relationships Attributes E/R Diagrams.
Database Design: ER Modelling (Continued) Reading: C&B, Chaps 11,12&16.
Author: Graeme C. Simsion and Graham C. Witt Chapter 5 Attributes and Columns.
© 2005 by Prentice Hall 1 Chapter 1: The Database Environment Modern Database Management 7 th Edition Jeffrey A. Hoffer, Mary B. Prescott, Fred R. McFadden.
1 UML and Classes, Objects and Relationships  Defining Domain Models Using Class Diagrams.
Author: Graeme C. Simsion and Graham C. Witt Chapter 4 Subtypes & Supertypes.
McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved. Chapter 10 Object-Oriented Analysis and Modeling Using the UML.
DataBase Data Modeling Using the Entity-Relationship Model.
+ Chapter 17 Database Design Using the REA Data Model Copyright © 2012 Pearson Education, Inc. publishing as Prentice Hall 17-1.
Database Design. miniworld Requirements & collection analysis Conceptual Design Data Model Mapping Physical Design Database Requirements Conceptual Schema.
Functional Dependencies and Normalization for Relational Databases.
1 Notes content copyright © 2004 Ian Sommerville. NU-specific content copyright © 2004 M. E. Kabay. All rights reserved. System Models IS301 – Software.
ITS232 Introduction To Database Management Systems Siti Nurbaya Ismail Faculty of Computer Science & Mathematics, Universiti Teknologi MARA (UiTM), Kedah.
BIS Database Systems School of Management, Business Information Systems, Assumption University A.Thanop Somprasong Chapter # 4 Entity Relationship.
Monica Farrow EM G30 Material on Vision Er 1 F28DM: Database Management Systems The Entity Relationship Model.
Data Analysis 1 Chapter 2.1 V3.1 Napier University Dr Gordon Russell.
Lecture 7 Enhanced Entity-Relationship Modelling & Advanced Normalisation.
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