1 / 11

Chapter 11 & 12 Entity-Relationship (E-R) Model

Chapter 11 & 12 Entity-Relationship (E-R) Model. Characteristics of E-R Model Components of E-R Model Example of E-R Model Enhanced E-R Model. Characteristics of E-R Model. Semantic data model Express the logical properties of an enterprise database

moe
Download Presentation

Chapter 11 & 12 Entity-Relationship (E-R) Model

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 11 & 12Entity-Relationship (E-R) Model • Characteristics of E-R Model • Components of E-R Model • Example of E-R Model • Enhanced E-R Model

  2. Characteristics of E-R Model • Semantic data model • Express the logical properties of an enterprise database • Design tools and documentation for data base structure • No physical DBMS • Proposed by Dr. Peter Chen

  3. Components of E-R Model • Entity • Attribute • Key • Relationship • Structural constraints on relationship

  4. Entity • Definition • An object or concept • Types • Strong entity (parent, owner, dominant) • Weak entity (child, dependent, or subordinate) • Diagram Notation • Rectangular

  5. Attribute • Domain • Types • Single • Composite • Single-valued • Multi-valued • Derived

  6. Key • Candidate key • Primary key • Composite key • Alternative key

  7. Relationship • Definition • Association among entities • Diagram Notation • Line – (role name) • Degree of a relationship • number of participating entities • types • Unary (recursive relationship) • Binary • Ternary • Quaternary

  8. Structural Constraints on Relationship • Cardinality constraints • Zero-to-one 0..1 • Zero-to-many 0..* • One-to-many 1..* • Many-to-many *..* • Participation constraints • Total (mandatory, every one involved) • Partial (optional, only some involved) • Improper relationship • Fan trap • Chasm trap

  9. Enhanced Entity-Relationship Model • Additional entity types • Superclass (generalization) • Subclass (specialization) • Constraints • Participation (mandatory, optional) • Disjoint: disjoint (or), non-disjoint (and) • Attribute Inheritance • Specialization hierarchy • Generalization hierarchy • Other • Aggregation (has a or is part of) • Composition (strong ownership of aggregation)

  10. Design Steps • Identify • Entity types, relationship types • Cardinality and participation constraints • Attributes • Keys • Specialize/generalize • EER diagram • EER model example

  11. Assignment • Review chapters 9-12 • Read chapter 13 • Homework assignment • 11.11 (enhanced e-r diagram) • Due date:

More Related