Chapter Two ( Data Model) Objectives Introduction to Data Models What are the Data Models Why they...
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Transcript of Chapter Two ( Data Model) Objectives Introduction to Data Models What are the Data Models Why they...
Chapter Two( Data Model)
Objectives Introduction to Data Models What are the Data Models Why they are important Learn how to design a DBMS
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Data Model: Model: Importance of data model:
Relatively simple representations, usually graphical, of complex real-world data structures
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Data Model:
Facilitate interaction among the designer(s), the applications programmer(s), and the end user(s)
Database Models:
Hierarchical Model Network Model Relational Model Entity Relationship (ER) Model
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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.
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Entity-Relationship Model (ER-Model)
A set of basic objects called Entity, and a set of Relationships among objects (Entities)
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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)
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Entity and Entity Set: (Continued)
An entity is represented by a set of attributesStudent(Name, Id, Gpa)
Each attribute has a set of permitted values called Domain (value set)Id: positive integer
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Relationship and Relationship Sets:
Relationship is an association among two or more entities
Faculty and Course
Relationship Set: is a set of similar relationships
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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
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Sources of Business Rules: Company managers Policy makers Department managers Written documentation
Procedures Standards Operations manuals
Direct interviews with the end users
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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
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Steps in designing a database using ER Model
1. Identifya. Entity setsb. Relationship sets
2. Identify semantic Info. In the relationship sets
3. Define the value sets of attributes4. Organize data into Entity/Relationships
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Database Lifecycle
1. Analysis: Study and analyze business
requirements Interview managers and users for
the information requirements Develop a system specification
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Database Lifecycle
2. Design (Data Models) Entity relational model (ER) Unify modeling language (UML)
Check the design
3. Build the Databases/Document/Test Create tables and views, and programs Produce manuals
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Database Life Cycle
4. Product delivery Load the software Monitor the performance
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Practice (Analysis):
Discuss a database system for an organization: