I&I_3_10 - CHAPTER 3 ORGANIZING DATA AND INFORMATION...

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CHAPTER 3 ORGANIZING DATA AND INFORMATION (Chapter 3, p. 68)
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Marina G. Erechtchoukova 2 Data Hierarchy A bit A byte (8 bits) represents a character : basic building unit of data A field - a logical grouping of characters A record - a logical grouping of related fields A file - a logical grouping of related records A database - a logical grouping of related files Character – field – record – file - database
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Marina G. Erechtchoukova 3 Storing and Accessing Records Direct Access Method – data are accessed directly without the necessity to read and discard other data index lists the key fields of each record and where that record is physically located in storage Sequential Access Method – data are accessed the order in which the data were stored Indexed Sequential Access Method (ISAM)
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Marina G. Erechtchoukova 4 File Environment An organization has multiple applications with related data Each application requires specific data format It is necessary to transform the data file from one format to another
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Marina G. Erechtchoukova 5 File Systems Input Output Application program Data file
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Marina G. Erechtchoukova 6 Data redundancy - a DBMS reduces data redundancy Data inconsistency – a DBMS provides better ways for data modification Violation of data integrity – a DBMS maintains data integrity Data isolation – a DBMS improves access to data Violation of application/data independence a DBMS supports data and program independence Problems with the File Environment
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Marina G. Erechtchoukova 7 DBMS History Generalized Update Access Method (at the beginning of 60s) Integrated Data Store (at the beginning of 60s) GUAM is transformed into Information Management System (in the middle of 60s) Data Base Task Group (1965)
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Marina G. Erechtchoukova 8 DBMS History (continued…) Relational data model had been introduced by Codd (1970) – second- generation DBMSs Third-generation DBMSs: Object- Oriented and Object-Relational Multidimensional data model Semistructured data model
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Marina G. Erechtchoukova 9 Database architecture Centralized database Distributed database replicated database Database: the Modern Approach
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Marina G. Erechtchoukova 10 Conceptual design - description of the database from user’s perspective using semantic data models Logical design – a model of a database showing data organization based on a given DBMS Physical design - shows the way a database is actually arranged on secondary storage devices Creating a Database
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Marina G. Erechtchoukova 11 Database Concepts
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This note was uploaded on 02/05/2012 for the course ECON 4140 taught by Professor A during the Spring '11 term at York University.

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I&I_3_10 - CHAPTER 3 ORGANIZING DATA AND INFORMATION...

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