Chapter 2 - Chapter2:DataModels Note There's minimal...

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Chapter 2: Data Models Note There's minimal coverage of Hierarichcal and Network models as I consider them of historical importance only Topics Business rules Data models o About the basic data-modeling building blocks o How the major data models evolved, and their advantages and disadvantages o How data models can be classified by level of abstraction Business Rules A policy, procedure, or principle within a specific organization's environment Applies 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 Sometimes are external to the organization Describe characteristics of the data as viewed by the company Business Rules (cont) Must be rendered in writing Brief, precise, unambiguous Must be kept up to date Must be easy to understand and widely disseminated Sources of Business Rules Company managers Policy makers Department managers Written documentation o Procedures o Standards o Operations manuals Direct interviews with end users Importance of Business Rules
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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 The Importance of Data Models Good database design uses an appropriate data model as its foundation End-users have different views and needs for data Data model organizes data for various users 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 Data Model Building Blocks Entity Anything about which data are to be collected and stored Attribute A characteristic of an entity (e.g. last name) Relationship 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 The Evolution of Data Models Hierarchical Network Relational Entity relationship Object oriented Crucial Database Components
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Schema Conceptual organization of entire database as viewed by the database administrator Subschema Defines database portion "seen" by the application programs that actually produce the desired information from data contained within the database Data Definition Language (DDL) Define data characteristics and data structure in order to manipulate the data DML Concepts Schema Data Definition Language (DDL)
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This note was uploaded on 10/25/2010 for the course CMPN SEM4 taught by Professor Thakur during the Spring '07 term at University of Mumbai.

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Chapter 2 - Chapter2:DataModels Note There's minimal...

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