Web-Enabled Decision Support Systems Introduction to Databases Prof. Name name@email.com Position (123) 456-7890 University Name

Overview 2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

Introduction The desire to collect, organize, and easily access information predates computer technology Oral records Written records (books) Computers, like books, have altered the way we collect, store, and retrieve information A database is a computer solution for fast, efficient, accurate, and secure data access Play a crucial role in the growing dominance of internet-based technology Used for a variety of purposes: Online shopping Driving directions Class enrollment and online grades

Overview 2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

Data The term data refers to known facts that can be recorded and preserved Include text, graphics, images, and/or video Data in Context

Information Information is the processed data presented in a form suitable for human interpretation The same data can be processed in a variety of ways to generate different kinds of information Information – Pie Chart

Metadata Metadata is data about data Process of information building demands an additional description of data to be processed Metadata

Overview 2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

Evolution of Database Systems Two approaches to convert data to information: File-based Developed in 1980’s Stores, manipulates, retrieves data from large flat files Database (relational systems) Developed by E. F. Codd of IBM in the early 1980's Widely used today Evolution of Database Systems

File-Based Approach A file is a collection of related information A system of files and collection of application programs manipulating them is a file-based system The University’s File-Based System

Limitations of File-Based Approach Efforts for query answering: What is the average grade for Dr. John Doe’s students? List the activities for all students enrolled in EZZ 4162. Which personnel are students as well as staff? Other limitations: Duplication of data Data dependency Slow development, high maintenance and fixed queries

Overview 2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

The Database System Limitations of file-based approach tell us that: Parameters defining data should be separately stored There should be a way to control and manipulate data in isolation of the application program A database management system (DBMS) is a piece of software that allows a user to define, create, and manage access to a database Decouples application programs from data The database stores all its data in one location, thereby limiting data duplication A database system can be defined as the combination of a database, a DBMS, and application programs Because of the advantages offered by a DBMS, businesses and organizations prefer the database approach to the file-based approach

University’s Database System

Components of a Database System There are four components in any database system: Users Database application DBMS Database Components of a Database System

Components of a Database System (cont.) A collection of logically related data Database management system (DBMS): Software that allows users to define, create, and manage database access Popular database management systems: Access, Oracle, IBM’s DB2, and SQL Server Database applications: Computer programs that allow users to manipulate the data in a DBMS through a user-friendly interface Can be divided into four broad categories: Personal: Restricted to a single user Departmental: Referenced by hundreds of users over a shared system or network Enterprise: Extensions of departmental applications involving thousands of users Internet: Largest form of information sharing wherein billions of users are involved

Components of a Database System (cont.) Database administrator, system developer, and end user: A database administrator (DBA) is a person responsible for all the data resources of an organization Uses tools that come with a DBMS to improve the productivity and performance of database planning and design System developers are a group of people responsible for the creation of new application programs that cater to the user requirements Use their own tools to write programs that communicate with the DBMS End-users in an organization can add, update, and delete data in a database through application programs or directly through a DBMS Use the application program to accomplish their day-to-day tasks

Functions of a DBMS A DBMS is primarily responsible for providing a logical view of underlying data Allows its user to store, retrieve, and update data in the database Provides a clear and logical view of the process that manipulates the data Other functionalities: Data independence Maintain segregation between the program and the data Concurrency control Recovery services Utility services Perform initialization and maintenance operations on a database

Advantages and Disadvantages of Database Approach Segregation of the application program and the data Minimal data duplication Ability to retrieve data easily Reduced development time and maintenance needs Disadvantages: Complexity Size Cost

Overview 2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

Database Development Process Enterprise modeling: Describes the data needed for database system Conceptual database modeling: Entity-relationship (E-R) modeling Logical database design: Relational data modeling is used to transform the E-R diagram into a relational schema Physical database design and creation: Selection of software (DBMS) and hardware

Schema The process of database development can also be explained using schema, an overall description of the database Three types of schemas, defined by their levels of abstraction: External schema: Describes the database in terms of data viewed by different users Conceptual schema: Describes the database in terms of entities, attributes, and relationships, along with its integrity constraints Internal schema: Describes the database in terms of stored records, data fields, and indexes

Three-Tier Architecture

Database Development Process

Overview 2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

Data Models A data model is a collection of concepts for describing data, its relationships, and its constraints Provides a clearer and more accurate description and representation of data Standard platform that enables database designers and end-users to communicate Come in three varieties: Object-based models (conceptual schema) Record-based models (external schema) Physical data models (internal schema)

Object-Based Data Models Object-based data models use entities, attributes, and relationships to present information An entity is a living or non-living object in the real world Examples: Person, place, event An attribute is a property of an entity Examples: Name, address of a person A relationship is an association between entities Example: Register is a relationship between student and courses Some common types of object-based data models include: Entity-relationship data model Functional data model Object-oriented data model

Entity-Relationship Data Model The entity-relationship model has emerged as one of the most popular and widely used techniques in today's databases Describes data in the form of an E-R diagram: Entities are rectangles (“Student” and “Department”) Relationships are diamonds (“Belongs to”) Attributes are ovals (“SSN”, “Name”) Cardinalities are constraints on relationships (“>” and “|”) Entity-Relationship Diagram

Record-Based Data Models Record-based data models use records to present data A record is a structure that contains a fixed number of fields to hold a piece of information There are three main types of record-based data models: Relational data models Based on mathematical concepts of relations Use tables (or relations) to represent data and relationships Network data models Hierarchical data models

Relational Data Models Each table consists of a fixed number of named columns (attributes) and an arbitrary number of unnamed rows (records) University Relational Data Model

Transforming the E-R Data Model to the Relational Data Model The E-R model and the relational model are actually closely related: Entities in the E-R model become tables in the relational model Attributes of in the E-R model are the table columns in the relational model Relationships in the E-R model are represented by a common attribute

Overview 2.1 Introduction 2.2 Data, Information, and Metadata 2.3 File-Based Approach 2.4 Database Approach 2.5 Database Development Process 2.6 Data Models 2.7 Summary

Summary Data are known facts that can be recorded and preserved Information is the processed data presented in a form suitable for human interpretation Metadata is data about data There are two approaches to convert data to information: Traditional file-based approach A system of files and the collection of computer programs manipulating them Modern database approach A database system consists of a combination of a database, a DBMS, and application programs

Summary (cont.) A database is an organized collection of logically related data. A database management system is software that allows users to define, create, and manage database access. Database applications are computer programs that allow users to manipulate data in a DBMS through a user-friendly interface. A database administrator (DBA) is a person or group of people responsible for all the data resources of an organization.

Summary (cont.) The database development process consists of four steps: Enterprise modeling Conceptual database modeling Logical database design Physical database design and creation The process of database development can also be explained through the schema, an overall description of the database External schema: Describes the database in terms of data viewed by different users Conceptual schema: Describes the database in terms of entities, attributes, and relationships along with integrity constraints Internal schema: Describes the database in terms of stored records, data fields, and indexes

Summary (cont.) A data model is a collection of concepts for describing data, its relationships, and its constraints Object-based data models use entities, attributes, and relationships to present information The entity-relationship data model is an example of object-based model and describes data in the form of an E-R diagram Record-based data models use records to present data Relational data model is based on mathematical concepts of relations and is an example of record-based model

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