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

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 Customer ID Customer Name Customer Location Product ID C1 Chrysler Germany 001 C2 Circuit City California H1 Hyundai Korea G1 GM Michigan 002 F1 Ford Motors H2 Honda Japan 003 B1 BMW Customers

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