IS605/606: Information Systems Instructor: Dr. Boris Jukic Relational Database Systems in Enterprise Information Systems.

IS605/606: Information

Systems Instructor: Dr. Boris Jukic

Relational Database Systems in Enterprise Information Systems

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

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

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

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

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

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

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

Relational Schema

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

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.

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

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.

Keys and Relationships: transaction processing system example

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

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

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

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

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

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

DATABASE MANAGEMENT SYSTEMS Database management systems (DBMS) –

software through which users and application programs interact with a database

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

INTEGRATING INFORMATION AMONG MULTIPLE DATABASES Forward integration – takes information entered into a given system

and sends it automatically to all downstream systems and processes

INTEGRATING INFORMATION AMONG MULTIPLE DATABASES Backward integration – takes information entered into a given system

and sends it automatically to all upstream systems and processes

INTEGRATING INFORMATION AMONG MULTIPLE DATABASES

Building a central repository specifically for integrated information