IS605/606: Information Systems Instructor: Dr. Boris Jukic
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Transcript of IS605/606: Information Systems Instructor: Dr. Boris Jukic
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IS605/606: Information
Systems Instructor: Dr. Boris Jukic
Relational Database Systems in Enterprise Information Systems
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File systems
File systems rely on coded file management programs to access, insert and modify their content
As such, file systems are plagued by two main problems Structural dependence refers to the fact that if a file structure is
changed (such as deletion or addition of a field), the related file management programs have to be modified accordingly
Data dependence refers to the fact that the changes in data characteristics, such as changing a field from integer to decimal (or even just changing the length of the field), will cause the related file management programs to be changed
Finally, there is a problem of data redundancy
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Data Redundancy
When the same data is stored in more than one location (in multiple files or multiple fields within one file) It may lead to: Data integrity (inconsistency) problems
may be caused by either data entry errors or failure to update all multiple copies of the same data
Data anomalies: modification, insertion and deletion
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Data Redundancy in File Systems and Resulting Anomalies
Modification anomaly: if PlainSounder model description changes
Insertion Anomaly: if a new customer (Toyota for example) is added to the list of those who buy BetterBox product
Product ID Product Name Product Description Product Price Customer ID Customer Name Customer Location Quantity Sold001 PlainSounder AM/FM Radio, 2 speakers $51 C1 Chrysler Corp Germany 15000001 PlainSounder AM/FM Radio, 2 speakers $51 C2 Circuit City California 18400001 PlainSounder AM/FM Radio, 2 speakers $51 H1 Hyundai Korea 26500002 BetterBox Radio, CD, 6 Speakers $123 G1 GM Michigan 23650002 BetterBox Radio, CD, 6 Speakers $123 F1 Ford Motors Michigan 14000003 UltraX CD, MP3, 8 Speakers $270 H2 Honda Japan 7500003 UltraX CD, MP3, 8 Speakers $270 B1 BMW Germany 2560
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Database Systems
Database Systems achieve data independence and structural independence If data type of as filed is changed or a field is eliminated or
a new one added, the existing management programs (queries) do NOT have to be modified
If properly designed, databases have a low level of redundancy, eliminating most of the insertion, deletion and modification anomalies
Logically related data instead of physically separated and unrelated files
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Four (Logical) Data Models
Hierarchical Model (Legacy) Standard tree-like structure
Network Model (Legacy) More than one parent allowed
Relational Model First truly data and structurally independent model No predetermined navigational maps as in two older
models The Database technology of choice
Object Model Tables become objects
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RELATIONAL DATABASE ADVANTAGES Database advantages from a business
perspective include Increased flexibility Increased scalability and performance Reduced information redundancy Increased information integrity (quality) Increased information security
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Relational Database Management System
In RMDBS, all data appears to be stored in a collection of tables (or relations), which are independent of one another, but can be linked through common entries in one of the tables' columns or fields (controlled redundancy)
Relational Schema: The graph depicting relationship types between tables
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Relational Schema
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Reduced Data Redundancy
Products Product Id Product Name Product Description Product Price
001 PlainSounder AM/FM Radio, 2 speakers $51.00
002 BetterBox Radio, CD, 6 Speakers $123.00
003 UltraX CD, MP3, 8 Speakers $270.00
Customers Customer ID
Customer Name
Customer Location
Product ID
C1 Chrysler Germany 001
C2 Circuit City California 001
H1 Hyundai Korea 001
G1 GM Michigan 002
F1 Ford Motors Michigan 002
H2 Honda Japan 003
B1 BMW Germany 003
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Tables in RDBMS
Tables: Logical constructs containing individual entity sets. Tables are always two-dimensional: rows and columns
each row represents a single entity (or entity instance) from the entity set
each (uniquely named) column represents one attribute each row-column intersection results in a single data value
Each table must have a primary key : An attribute uniquely identifying each row (entity), satisfying the entity integrity conditions. Null value (no entry) is not permitted for a primary key.
The order of rows and columns within the table is irrelevant Foreign Key is an attribute in one table whose values must
either match the value of a primary key in another table or be set to null (no value). These conditions are known as referential integrity constraint.
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Relationships within the relational database:
• One-to-one relationships: • One-to many relationships:
• Examples: • professor - class • department - employee
• Many to-many relationships• Examples: parts – product, student – class, …• it is recommended to break it into a set
(usually two) of one-to-may relationships through a so called composite (bridge) entity
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Enterprise data planning
• A large component of the business informational needs can be captured by the mapping of all entities the organizations need to keep track of and the relationships among them• E-R (Entity-Relationship) modeling is a
standard technique that provides a simplified picture of the relationship among entities.
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Keys and Relationships: transaction processing system example
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RELATIONAL DATABASE ADVANTAGES Database advantages from a business
perspective include Increased flexibility Increased scalability and performance Reduced information redundancy Increased information integrity (quality) Increased information security
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Increased Flexibility
A well-designed database should: Handle changes quickly and easily Provide users with different views A database has only one physical view
Physical view – deals with the physical storage of information on a storage device such as a hard disk
A database can have multiple logical views Logical view – focuses on how users logically access
information to meet particular business needs
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Increased Scalability and Performance A database must scale to meet increased
demand, while maintaining acceptable performance levels Scalability – refers to how well a system can
adapt to increased demands Performance – measures how quickly a system
performs a certain process or transaction
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Reduced Information Redundancy Databases reduce information redundancy
Redundancy – the duplication of information or storing the same information in multiple places
Inconsistency is one of the primary problems with redundant information
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Increase Information Integrity (Quality) Information integrity – a measure of the quality of information
Integrity constraints – rules that help ensure the quality of information Operational integrity constraints – rules that enforce
basic and fundamental information-based constraints Business-critical integrity constraints – rules that
enforce business rules vital to an organization’s success and often require more insight and knowledge than operational integrity constraints
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Increased Information Security Information is an organizational asset and
must be protected
Databases offer several security features including: Passwords – provide authentication of the user Access levels – determine who has access to the
different types of information Access controls – Determine types of user access,
such as read-only access
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DATABASE MANAGEMENT SYSTEMS Database management systems (DBMS) –
software through which users and application programs interact with a database
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INTEGRATING INFORMATION AMONG MULTIPLE DATABASES Organizations typically maintain multiple
systems, each with its own database
Integration – allows separate systems to communicate directly with each other
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INTEGRATING INFORMATION AMONG MULTIPLE DATABASES Forward integration – takes information entered into a given system
and sends it automatically to all downstream systems and processes
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INTEGRATING INFORMATION AMONG MULTIPLE DATABASES Backward integration – takes information entered into a given system
and sends it automatically to all upstream systems and processes
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INTEGRATING INFORMATION AMONG MULTIPLE DATABASES
Building a central repository specifically for integrated information