Chapter2 - 2 Chapter 2 Data Model Database Systems: Design,...

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2 1 Chapter 2 Data Model Database Systems: Design, Implementation, and Management, Sixth Edition, Rob and Coronel
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2 2 In this chapter, you will learn: Why data models are important About the basic data-modeling building blocks What business rules are and how they affect database design How the major data models evolved, and their advantages and disadvantages How data models can be classified by level of abstraction
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2 3 The Importance of Data Models Data model Relatively simple representation, usually graphical, of complex real-world data structures Communications tool to facilitate interaction among the designer, the applications programmer, and the end user Good database design uses an appropriate data model as its foundation
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2 4 Importance of Data Modeling End-users have different views and needs for data Data model organizes data for various users
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2 5 Data Model Basic Building Blocks Entity is anything about which data are to be collected and stored (these become tables) Attribute is a characteristic of an entity (these become columns in the tables) Relationship describes an association among (two or more) entities One-to-many (1:M) relationship Many-to-many (M:N or M:M) relationship One-to-one (1:1) relationship
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2 6 Business Rules Brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization’s environment 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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2 7 Business Rules ( continued ) Must be rendered in writing Must be kept up to date Sometimes are external to the organization Must be easy to understand and widely disseminated Describe characteristics of the data as viewed by the company
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2 8 Sources of Business Rules Company managers Policy makers Department managers Written documentation Procedures Standards Operations manuals Direct interviews with end users
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2 9 Importance of Business Rules Promote creation of an accurate 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
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2 10 The Evolution of Data Models Hierarchical Network Relational Entity relationship Object oriented
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2 11 The Hierarchical Model—Evolution GUAM (Generalized Update Access Method) Based on the recognition that the many smaller parts would come together as components of still larger components Information Management System (IMS) World’s leading mainframe hierarchical database system in the 1970s and early 1980s
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2 12 The Hierarchical Model—Characteristics
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This note was uploaded on 10/10/2011 for the course CIS339 NONE taught by Professor None during the Spring '10 term at DeVry Chicago.

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Chapter2 - 2 Chapter 2 Data Model Database Systems: Design,...

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