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Fundamentals of Database Systems

• Book Title: Fundamentals of Database Systems
• Edition: 5th
• Authors: Elmasri / Navathe

Chapter 1: Introduction: Databases and Database Users

• Outline Topics:
  • Types of Databases and Database Applications
  • Basic Definitions
  • Typical DBMS Functionality
  • Example of a Database (UNIVERSITY)
  • Main Characteristics of the Database Approach
  • Database Users
  • Advantages of Using the Database Approach
  • When Not to Use Databases

Types of Databases and Database Applications

• Traditional Applications: Numeric and textual databases
• More Recent Applications: Multimedia databases, Geographic Information Systems (GIS), Data Warehouses, Real-time and Active Databases, many more
• Later chapters in book describe more recent database applications

Basic Definitions

• Database: A collection of related data.
• Data: Known facts that can be recorded, with implicit meaning.
• Mini-world: A portion of the real world, for example student grades at a University
• DBMS (Database Management System): Software system for creating, maintaining computerized databases
• Database System: DBMS software, the data itself, and sometimes applications

Simplified Database System Environment (Figure 1.1)

• Diagram shows layers of a simplified database system: Users/Programmers, Application Programs/Queries, DBMS Software, Software to Process Queries/Programs, Software to Access Stored Data, Stored Database Definition (Meta-Data)

Typical DBMS Functionality

• Defining Database Structures
• Constructing and Loading Initial Database Contents
• Manipulating the Database: Retrieval (e.g., querying, reporting), Modification (insertions, deletions, updates), Accessing through Web Applications
• Processing and Sharing: By concurrent users and application programs; maintain data validity and consistency
• Other features: Security Measures (prevent unauthorized access), Active Processing (internal actions on data), Presentation and Visualization, Maintenance (database and associated programs throughout the lifetime)

Example of a Database (UNIVERSITY)

• Mini-world: Part of a university environment
• Entities:
  • STUDENTS
  • COURSES
  • SECTIONS
  • DEPARTMENTS
  • INSTRUCTORS

Example of Mini-world Relationships

• SECTIONS are of specific COURSES
• STUDENTS take SECTIONS
• COURSES have prerequisite COURSES
• INSTRUCTORS teach SECTIONS
• COURSES are offered by DEPARTMENTS
• STUDENTS major in DEPARTMENTS

Example of a Simple Database (Figure 1.2)

• Shows sample data for COURSES, SECTIONS, and GRADE REPORT tables
• Includes a PREREQUISITE table

Main Characteristics of the Database Approach

• Self-describing nature: DBMS catalog stores data structure details, types/constraints (meta-data), allowing DBMS to work with different database applications.
• Insulation: Program-Data Independence; allows changing data structures/storage organization without modifying DBMS access programs.
• Example simplified database catalog (Figure 1.3): Shows how relations, columns, associated data types, and relations are defined

Data Abstraction

• Using data models to hide storage details from users, presenting a conceptual view of the database to users
• Programs often refer to data model constructs, not storage details
• Allows multiple views of same database for different users, showing only pertinent information

Sharing of Data and Multi-user Transaction Processing

• Allowing multiple concurrent users to retrieve and update data.
• The DBMS ensures each transaction is processed correctly or aborted
• Recovery subsystem to record changes permanently
• Online Transaction Processing (OLTP) facilitates hundreds of concurrent user transactions per second

Database Users

• Actors on the Scene: Users who interact with/control database content.
  • Those who design, develop, and maintain applications
• Workers Behind the Scene:
  • Database Administrators: Authorize access, coordinate use, and manage resources
  • Database Designers: Define content, structure, and constraints; communicate with end-users

Categories of End-Users

• Casual: Access database occasionally
• Naïve/Parametric: Use predefined functions (e.g., bank tellers, reservation clerks)
• Sophisticated: Business analysts, scientists, engineers; use tools that closely interact with database
• Stand-alone: Maintain personal databases using packaged applications (e.g., tax programs, address books)

Advantages of Using the Database Approach

• Controlling data redundancy
• Sharing data among multiple users
• Restricting unauthorized access
• Providing persistent storage for program objects
• Providing structured storage (e.g., indexes) for efficient query processing
• Backup and recovery services
• Providing multiple user interfaces
• Representing complex relationships among data
• Enforcing integrity constraints
• Drawing inferences and taking actions from stored data

Additional Implications of Using the Database Approach

• Enforcing standards (e.g., data item names, display formats)
• Reduced application development time by reducing time added to each new application
• Flexibility to change database structures
• Availability of current information important for online transaction systems (e.g., airline/hotel bookings)
• Economies of scale (avoid wasteful resource duplication)

Historical Development of Database Technology

• Early Database Applications (Hierarchical and Network Models – 1960s-1970s)
• Relational Model (1970s)
• Object-Oriented and Emerging Applications (OODBMSs, ORDBMSs in 1980s-1990s)

Evolution of DB Systems (Figure 1.26)

• Shows progression through different types of databases over time

Example of Network Model Schema (Figure 2.8)

• Illustrates network database model using a diagram

Flat Database Example (Figure 1.28)

• Provides and example of data in a flat database

Network & Hierarchical Database (Figure 1.29)

• Hierarchical Database Structure Diagram

Relational & Object-oriented Database Model (Figure 1.30)

• Database model diagrams for relational and object-oriented models

Extending Database Capabilities

• Additional functionalities being added to DBMSs
  • Scientific applications, XML, image/audio/video management, data warehousing/mining, spatial data management, time series management
• Leads to new types of data, complex structures, and indexing schemes

When Not to Use a DBMS

• Main Inhibitors (Costs): Large initial investment in hardware and software; administrative overhead for database functions
• DBMS may be unnecessary: If database/applications are simple, well-defined, and not expected to change; if access by multiple users isn't needed