Database Systems

Chapter 1: Database Systems

• This chapter introduces database systems, covering the difference between data and information, database types, and their importance in decision-making.
• It also details the evolution of modern databases from file systems, highlighting the flaws in file system data management and the main components/functions of a DBMS.
• Learning outcomes include understanding data and information, database types, the importance of database design, and the history of databases from file systems.

Introduction

• Good decisions are informed by good information derived from facts.
• Data management is most efficient when stored in a database.
• Databases evolved from computer file systems.
• Understanding file system characteristics is crucial for database design.

Why Databases?

• Databases address problems encountered in data management, crucial in business, research, and administration.
• Understanding databases and their interaction with other applications is vital.

Data vs. Information

• Data are raw facts, while information is the result of processing data to reveal meaning.
• Information requires context to have meaning.
• Raw data requires formatting for storage, processing, and presentation.
• Data forms the foundation of information and information forms the bedrock of knowledge.

Introducing the Database

• A database is a shared and integrated computer structure holding end-user data (raw facts of interest to users), and metadata (data about data, describing data characteristics and relationships).
• Metadata describes data characteristics and relationships, or the content of an item.
• Metadata can describe images (size, color, resolution, creation date), and text documents (length, author, writing date, summary).
• Web pages often include metadata in the form of meta-tags (description and keywords).

Role and Advantages of the DBMS

• A DBMS (Database Management System) is a program collection managing structure and controlling data access.
• It's an intermediary between the user and the database.
• The database structure is stored as a file collection, accessed only via the DBMS.
• A DBMS enables data sharing and integrates views of data from multiple users.

Advantages of a DBMS

• Improved data sharing
• Improved data security
• Better data integration
• Minimized data inconsistency
• Improved data access
• Improved decision-making
• Increased end-user productivity

Types of Databases

• Databases are classified by users (single-user, multiuser), location (centralized, distributed/decentralized), and usage (operational, data warehouse).
• A single-user database only supports one user at a time (e.g., ATM).
• A multiuser database supports multiple users simultaneously (e.g., i-student portals).
• Centralized databases store data at a single site, while distributed/decentralizeddatabases store data across multiple sites.

Categories of Data

• Structured data is organized in a structure, like a database.
• Semi-structured data has some structure but may lack the complete structure to be considered totally structured. (e.g. XML).
• Unstructured data is in its original format and is not part of a recognizable database structure (e.g. bitmap images).

Why Database Design Is Important

• Database design focuses on the structure of end-user data.
• Designers must identify the database's expected use.
• Well-designed databases facilitate data management and accurate information.
• Poor design causes difficult-to-trace errors.

Evolution of File System Data Processing

• File systems are easier to understand than database design.
• Understanding file system problems helps avoid DBMS issues.
• File systems are useful when converting to database systems
• File systems consist of collections of file folders, each tagged and organized by expected use.

Problems with File System Data Processing

• File systems are prone to security breaches.
• Many problems in file systems are repeated in larger, more complex systems.
• File system retrieval requires extensive programming.
• Ad hoc queries are difficult to execute, making them not as adaptable to changing user needs.

Structural and Data Dependence

• Structural dependence: database changes affect the ability of DBMS programs to access data. All programs must be changed if the database structure changes.
• Structural Independence: data access is not affected by changes in database structure.
• Data-dependent Data Access Changes: data access changes when the method or location of data storage changes (e.g., changes in file structure).
• Data-independent Data Storage Changes: changes in data storage don't affect data access (data and programs are separated).

Data Redundancy

• File system structure makes it hard to combine data from multiple sources, making it vulnerable to security breaches.
• Data is often stored in different locations with similar information, causing update or deletion issues.
• Data redundancy: same data stored in multiple places.
• Data inconsistency means many versions of the same data in different places.

Data anomalies

• Anomalies arise when changes in redundant data are not made correctly in all related locations, leading to inconsistencies.

Lack of Design and Data-Modeling Skills

• Most people lack the skill to properly design databases, often relying on productivity tools.
• Strong data modeling skills help communication between designers, users, and developers.

Database Systems

• Database systems, which consist of logically related data stored in a single repository, solve many of the file system problems.
• Current database systems store data structures, relationships, and access paths, enabling the separate storage of the structure and the data.

The Database System Environment

• The database system is a collection of hardware, software, data, procedures, and people.
• The hardware consists of physical devices required to run the system.
• The software is operating system software, DBMS software, application programs, and utility software.
• Data consists of the collection of facts stored in the system.
• People are all users, administrators, designers, analysts, and programmers.
• Procedures involve the instructions and rules for designing and using the database.

DBMS Functions

• DBMS functions are mostly transparent to end users.
• Data dictionary management: storing and maintaining data definitions.
• Data storage management: creating and managing complex structures for data storage.
• Data transformation and presentation: transforming and presenting data for user needs.
• Security management: enforcing security rules and data privacy.
• Multiuser access control: managing concurrent access.
• Backup and recovery management: managing data safety and recovery.
• Data integrity management: enforcing data rules and minimizing redundancy.
• Database access languages and application programming interfaces: providing tools for interacting with the database.
• Database communication interfaces: allowing various communication types (e.g., web interfaces, email distribution).
• Metadata (data about data) is an important part of a DBMS, defining the database structure.

Managing the Database System

• Database systems provide a framework that enforces strict procedures and standards, shifting the role of people from programming to resource management.
• Databases facilitate more sophisticated and effective data use.
• Data structures and relationships determine the effectiveness of the database.