Database Types, Applications, and Definitions

Types of databases and database applications

• Traditional database applications store textual or numeric information
• Multimedia databases store images, audio clips, and video streams digitally
• Geographic Information Systems (GIS) store and analyze maps, weather data, and satellite images
• Data warehouses and Online Analytical Processing (OLAP) systems are used to extract and analyze useful business information from very large databases to support decision-making

Basic definitions

• Data refers to known facts that can be recorded and have an implicit meaning
• A database represents a collection of related data
• A mini-world represents some aspect of the real world, such as student grades at a university
• Mini-worlds must be built for a specific purpose
• The database should accurately reflect the mini-world it represents

Database Management System (DBMS)

• The DBMS is a collection of programs that enables users to create and maintain a database
• It facilitates defining, constructing, manipulating, and sharing databases
• Defining involves specifying data types, structures, and constraints of data stored in the database
• Constructing refers to the process of storing data on some storage medium controlled by the DBMS
• Manipulating involves querying the database to retrieve specific data
• Manipulating also involves updating the database to reflect changes in the mini-world
• Manipulating also involves generating reports from the data
• Sharing enables multiple users and programs to access the database at the same time
• Security measures that prevent unauthorized access must be included
• Features include protection from software or hardware failure
• Features include presentation and visualization of data
• The DBMS maintains the database and its associated programs throughout the application's lifetime
• Database definition is stored by the DBMS in a database catalog or dictionary
• The DBMS allows users to define a database through a Data Definition Language (DDL)
• The DBMS allows users to insert, update, delete, and retrieve data through Data Manipulation Language (DML)

Database approach vs file processing

• Problems with the file processing approach include data redundancy and inconsistency
• Data redundancy is defined the presence of duplicate data in multiple files
• Data inconsistency is when the same attribute has different values
• File processing lead to a waste of storage space and redundant efforts to maintain up-to-date data
• Program-data dependence is an issue because each user defines and implements the files needed for a specific application
• File structure is defined in the program code
• Problems with file processing include limited data sharing
• Problems include a lack of centralized control of data
• Problems include lengthy development times, as programmers must design file formats
• Poor security is an issue because file processing systems rely on file-system level security, allowing anyone with access to read or modify data

Characteristics of the database approach

• Database systems have a self-describing nature
• The database system consist of the database and meta-data
• Metadata refers to the DB definition
• Metadata is stored in the DBMS catalog and it is used by the DBMS software and database users
• Insulation between programs and data, and data abstraction are characteristics
• Program-data independence mean data structures and storage organization can be changed without changing DBMS access programs
• Data abstraction is the characteristic that allows for program-data independence
• DBMS provides users with conceptual representation of data
• A data model is a type of data abstraction that is used to provide this conceptual representation
• The database approach supports of multiple views of the data
• This allows each user to have their own view of the database
• A view is essentially some subset of the database
• The multiple views reduce complexity
• The views provide a level of security
• The views provide a mechanism to customize the appearance of the database
• The database approach allows sharing of data and multi-user transaction processing
• It allows multiple users to access the database at the same time
• DBMS must include concurrency control, and it guarantees that each transaction is correctly executed or aborted
• The applications are generally called online transaction processing (OLTP) applications
• Isolation property of a transaction is that each transaction appears to execute in isolation from other transactions
• Atomicity property requires that either all the database operations in a transaction are executed or none are

Database Users

• The actors on the scene include the Database Administrator (DBA)
• DBAs authorize access to the database
• DBAs coordinate and monitors its use
• DBAs ensure to acquire software and hardware resources
• The Database Designer is another actor
• Database designers identify the data to be stored
• They also choose appropriate structures to represent and store this data
• End Users are also actor on the scene and they are people whose jobs require access to the database
• Casual end users are a type of end user
• Naive or parametric end users
• Sophisticated end users
• Standalone users
• System Analysts and Application Programmers
• They determine requirements of end users
• They implement these specifications as programs
• Workers behind the scenes include System designers and implementers
• These workers design and implement the DBMS modules and interfaces as a software package
• Tool developers design and implement tools
• Operators and maintenance personnel: are responsible for running and maintenance of hardware and software environment for database system

Components of DBMS Environment

• Hardware can range from a PC to a network of computers.
• Software is the DBMS, operating system, network software (if necessary) and also the application programs.
• Procedures are Instructions and rules that govern the design and use of the database and DBMS.