1. 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

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: