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02010_ch02 - Database Systems Design Implementation and...

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1 Database Systems, 8 th Edition Database Systems: Design, Implementation, and Management Eighth Edition Chapter 2 Data Models
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2 Database Systems, 8 th Edition Objectives About data modeling and why data models are important About the basic data-modeling building blocks What business rules are and how they influence database design How the major data models evolved How data models can be classified by level of abstraction
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3 Database Systems, 8 th Edition Introduction Designers, programmers, and end users see data in different ways Different views of same data lead to designs that do not reflect organization’s operation Data modeling reduces complexities of database design Various degrees of data abstraction help reconcile varying views of same data
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4 Database Systems, 8 th Edition Data Modeling and Data Models Data models Relatively simple representations of complex real-world data structures Often graphical Model: an abstraction of a real-world object or event Useful in understanding complexities of the real-world environment Data modeling is iterative and progressive
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5 Database Systems, 8 th Edition The Importance of Data Models Facilitate interaction among the designer, the applications programmer, and the end user End users have different views and needs for data Data model organizes data for various users Data model is an abstraction Cannot draw required data out of the data model
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6 Database Systems, 8 th Edition Data Model Basic Building Blocks Entity: anything about which data are to be collected and stored Attribute: a characteristic of an entity Relationship: describes an association among entities One-to-many (1:M) relationship Many-to-many (M:N or M:M) relationship One-to-one (1:1) relationship Constraint: a restriction placed on the data
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7 Database Systems, 8 th Edition Business Rules Descriptions of policies, procedures, or principles within a specific organization Apply to any organization that stores and uses data to generate information Description of operations to create/enforce actions within an organization’s environment Must be in writing and kept up to date Must be easy to understand and widely disseminated Describe characteristics of data as viewed by the company
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8 Database Systems, 8 th Edition Discovering Business Rules 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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9 Database Systems, 8 th Edition Discovering Business Rules (continued) Standardize company’s view of data 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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10 Database Systems, 8 th
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