Chapter Two ( Data Model)

1. Chapter Two( Data Model) Objectives Introduction to Data Models What are the Data Models Why they are important Learn how to design a DBMS

2. Data Model: • Model: • Importance of data model: • Relatively simple representations, usually graphical, of complex real-world data structures

3. Data Model: Facilitate interaction among the designer(s), the applications programmer(s), and the end user(s)

4. Database Models: Hierarchical Model Network Model Relational Model Entity Relationship (ER) Model

5. Entity-Relationship Model (ER-Model) Purpose of ER Model is to allow the description of an enterprise to be written without the attention to the efficiency or the physical design.

6. Entity-Relationship Model (ER-Model) • A set of basic objects called Entity, and a set of Relationships among objects (Entities)

7. Entity and Entity Set: Entity: • An object that exists and is distinguishable from other objects • Car ? • VW? • Entity Set: • A set of entities of the same type • Entity set needs not be disjoint (Faculty vs Student)

8. Entity and Entity Set: (Continued) • An entity is represented by a set of attributes Student(Name, Id, Gpa) • Each attribute has a set of permitted values called Domain (value set) Id: positive integer

9. Relationship and Relationship Sets: • Relationship is an association among two or more entities Faculty and Course • Relationship Set: is a set of similar relationships

10. Business Rules: • Brief, precise, and unambiguous descriptions of a policies, procedures, or principles within a specific organization • Apply to any organization that stores and uses data to generate information • Description of operations that help to create and enforce actions within that organization’s environment

11. Sources of Business Rules: • Company managers • Policy makers • Department managers • Written documentation • Procedures • Standards • Operations manuals • Direct interviews with the end users

12. Translating Business Rules into Data Model: • Standardize company’s view of data • Constitute a communications tool between users and designers • Allow designer to understand the nature, role, and scope of data • Allow designer to understand business processes • Allow designer to develop appropriate relationship participation rules and constraints • Promote creation of an accurate data model

13. Steps in designing a database using ER Model • Identify • Entity sets • Relationship sets • Identify semantic Info. In the relationship sets • Define the value sets of attributes • Organize data into Entity/Relationships

14. Database Lifecycle • Analysis: • Study and analyze business requirements • Interview managers and users for the information requirements • Develop a system specification

15. Database Lifecycle • Design (Data Models) • Entity relational model (ER) • Unify modeling language (UML) • Check the design • Build the Databases/Document/Test • Create tables and views, and programs • Produce manuals

16. Database Life Cycle • Product delivery • Load the software • Monitor the performance

17. Practice (Analysis): Discuss a database system for an organization: