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Data vs. Information
Data: Raw facts; building blocks of information Unprocessed information
Information: Data processed to reveal meaning
Accurate, relevant, and timely information is key to good decision making
Good decision making is key to survival in global environment
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Database definitions:
Def 1: A shared collection of logically related data, designed to meet the information needs of multiple users in an organization. The term database is often erroneously referred to as a synonym for a “database management system (DBMS)”. They are not equivalent and it will be explained in the next section.
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Database definitions (cont…)
Def 2: A collection of data: part numbers, product codes, customer information, etc. It usually refers to data organized and stored on a computer that can be searched and retrieved by a computer program.
Def 3: A data structure that stores metadata, i.e. data about data. More generally we can say an organized collection of information.
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Database definitions (cont…)
Def 4: A collection of information organized and presented to serve a specific purpose. (A telephone book is a common database.) A computerized database is an updated, organized file of machine readable information that is rapidly searched and retrieved by computer.
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Database definitions (cont…)
Def 5: An organized collection of information in computerized format.
Def 6: A collection of related information
about a subject organized in a useful manner that provides a base or foundation for procedures such as retrieving information, drawing conclusions, and making decisions.
Def 7: A Computerized representation of any organizations flow of information and storage of data.
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Types of Databases
Single-user:
Supports only one user at a time
Desktop/Personal Databases
Single-user database running on a personal computer
Multi-user:
Supports multiple users at the same time
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Types of Databases (continued)
Workgroup
Multi-user database that supports a small group of users or a single department
Enterprise
Multi-user database that supports a large group of users or an entire organization
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Location of Databases
Centralized:
Supports data located at a single site
Distributed:
Supports data distributed across several sites
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Disadvantages of File Processing
Program-Data Dependence All programs maintain metadata for each file they use
Duplication of Data Different systems/programs have separate copies of the same data
Limited Data Sharing No centralized control of data
Lengthy Development Times Programmers must design their own file formats
Excessive Program Maintenance 80% of information systems budget
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Problems with Data Dependency
Each application programmer must maintain their own data
Each application program needs to include code for the metadata of each file
Each application program must have its own processing routines for reading, inserting, updating and deleting data
Lack of coordination and central control Non-standard file formats
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Problems with Data Redundancy
Waste of space to have duplicate dataCauses more maintenance headachesThe biggest problem:
When data changes in one file, could cause inconsistencies
Compromises data integrity
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SOLUTION: The DATABASE Approach
Central repository of shared dataData is managed by a controlling
agentStored in a standardized,
convenient form
Requires a Database Management System (DBMS)
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Database Management System
DBMS manages data resources like an operating system manages hardware resources
A software system that is used to create, maintain, and provide controlled access to user databases
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Elements of the Database Approach
Enterprise Data Model Graphical model showing high-level entities
and relationships for the organization and the relationship among those entities.
Entity: an object or concept that is important to the business.
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One customer may place many orders, but each order is placed by a single customer
One-to-many relationship
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One order has many order lines; each order line is associated with a single order
One-to-many relationship
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One product can be in many order lines, each order line refers to a single product
One-to-many relationship
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Therefore, one order involves many products and one product is involved in many orders
Many-to-many relationship
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Elements of the Database Approach (cont…)
Relational DatabasesDatabase technology involving tables (relations) representing entities and primary/foreign keys representing relationships
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Elements of the Database Approach (cont…) Use of Internet Technology
Networks and telecommunications, distributed databases, client-server
Database Applications Application programs used to perform database
activities (create, read, update, and delete) for database users
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Application program functions: inserting new data, updating existing data, deleting existing data, reading data for display
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Advantages of Databases
Program-Data independence The separation of data description (metadata)
from application programs that use the data. Changing organization’s data with out
changing application programs that process that data.
Minimal data redundancy Previously separate data files are integrated
into a single, logical structure. Some limited redundancy may be desirable to
improve database performance.
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Advantages of Databases (cont…)
Improved data consistency By eliminating data redundancy we greatly
reduce inconsistencies. e.g. customer address stored once
Storage space is not wasted Increased productivity of application
development Cost and time of new database application
is reduced Using functions, using reports and forms
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Advantages of Databases (cont…)
Improved data quality Database designer can specify constraints
Improved data accessibility Select * from product where
product_name= “computer”; Reduced program maintenance
Changes are easily accommodated e.g. adding new data items, changing data formats
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Costs and risks of database approach
New, specialized personals Hire individuals to design and implement, and
administer databases Upgradation of personal if new technology comes to
market Installation and management cost
Install, new release and upgrades, costly software for security
Conversion cost Legacy system: older application in an organization
based on file processing system Legacy to modern
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Components of the Database Environment
CASE Tools – computer-aided software engineering Repository – centralized storehouse of metadata Database Management System (DBMS) – software for managing
the database Database – storehouse of the data Application Programs – software using the data User Interface – text and graphical displays to users Data Administrators – personnel responsible for maintaining the
database System Developers – personnel responsible for designing
databases and software End Users – people who use the applications and databases