class03b - Acct 360: 03b Data Modeling DBMSs and Databases...

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Acct 360: 03b Data Modeling
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DBMSs and Databases Why Do We Have DBMSs and Databases? When were they developed? What is the difference between a DBMS and a database?
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File Processing Systems (~1960) The tendency was to create a new file on magnetic tape with the appropriate data fields whenever a new report was needed. The corresponding application program was then "locked" to the data structure in the file. This caused terrific updating problems due to data and fact redundancy. There was, however, one advantage to all this redundancy -- it provided some insulation from disasters.
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Problems with File Systems Uncontrolled Duplication Inconsistent Data Inflexibility Limited Data Sharing Poor Enforcement of Standards Poor Programmer Productivity Excessive Program Maintenance
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What is a DBMS? A (large) piece of software which provides an interface between the user or application program and the database. A DBMS is developed according to a particular data model; it "fits" one model best. Some example DBMSs are Oracle, Access, DB2 Others include: Alpha Five, DataEase, FileMaker, Firebird, Ingres, Informix, Mark Logic, FoxPro PostreSQL, Progress, SQLite, Teradata, CSQL, OPenLink Vrtuoso, Daffodil DB, OpenOffice.org Base, etc.
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What is a Database? It is a logically coherent collection of data with inherent meaning. It is built for a purpose. It represents a “miniworld,” and should represent the state of that world accurately.
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DBMSs Database Database Engine Data Dictionary Security Query Processor Application Generator Form Builder Report Writer Communication Network 3GL Connector
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Data Modeling “We are not modeling reality, but the way information about reality is processed by people." Kent (1978) Data and Reality , p19.
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Data Models A data model is a way of representing (part of) the world. The main current data models are Hierarchical Network Relational Entity-relationship Object-oriented DBMSs typically implement one data model. IMS hierarchical IDMS network Oracle relational
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“Important Names” Bachman Network model 1960's Codd Relational model 1970 Chen Entity Relationship model 1976
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Queries The hard thing about retrieving data is deciding what question to ask, not asking it. Brooks, "No Silver Bullet” IEEE Computer , April 1987, p10-19
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Database Design What is database design? What is (are) the goal(s) of design? Why do databases need to be designed? Are there different approaches? Are there different levels? How can I tell if I have a good design?
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1) Minimize data redundancy 2) Eliminate fact redundancy 3) Represent the situation accurately The result of meeting Goals 1 and 2 is a database that has integrity. The result of additionally meeting Goal 3 is a
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This note was uploaded on 03/02/2010 for the course MATH 139 taught by Professor Tall during the Spring '08 term at SIU Carbondale.

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class03b - Acct 360: 03b Data Modeling DBMSs and Databases...

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