Chapter 1: Databases and Database Users

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Chapter 1 Databases and Database Users

• From Fundamentals of Database Systems by
  Elmasri/Navathe

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Database Applications

• Traditional Database Applications
• Mainly textual and numeric information
• Examples?
• Multimedia Databases
• Images, audio clips, video streams
• Geographic Information Systems
• Store/Analyze maps, weather data, satellite
  images

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Database Applications (contd)

• Data Warehouses and Online Analytical Processing
  (OLAP)
• Extract and analyze information to support
  decision making
• Real-Time and Active Database Technology
• Industrial and manufacturing processes

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Introduction

• Databases and Database Technology play a critical
  role in almost all areas where computers are used
• Business
• Electronic Commerce
• Engineering
• Medicine
• Law
• Education
• Library Science

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Terminology

• Database (general)
• Collection of related data
• Can be any size
• Maintained manually or computerized
• Data
• Known facts that can be recorded that have an
  implicit meaning
• Examples?

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Implicit Properties of Databases

• A database represents some aspect of the real
  world (miniworld or Universe of Discourse (UoD)
  ). Changes reflected
• Logically coherent (not random) collection with
  an inherent meaning
• Designed, built and populated for a specific
  purpose with an intended group of users and
  preconceived applications

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DBMS

• Database Management System (DBMS)
• General-purpose software system that facilitates
  the processes of
• Defining
• Constructing
• Manipulating
• Sharing
• Databases
• Four main characteristics we will look at more
  later

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Defining a Database

• Specify
• Data types
• Structures
• Constraints of the data to be stored in the
  database
• DDL Data Definition Language
• Meta-data
• Database definition. Information about the
  database itself is also stored in the database
  catalog (dictionary)

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DBMS (contd)

• Constructing a Database
• Storing the data on some storage medium that is
  controlled by the DBMS
• Manipulating a Database
• DML Data Manipulation Language
• Querying the data stored to reflect the changes
• Generate Reports from the data
• Sharing the Database (synchronization)
• Allow concurrent user access and data
  manipulation (e.g., one seat left in the plane
  and two passengers want to reserve it)

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Application Program

• Accesses the data in the database
• Several application programs may be in use
• Allows users to
• query data (retrieve/update/delete)
• generate reports

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DBMS (contd) Functions

• Transaction
• Will cause data to be read from and written to
  the database
• A series of queries that need to take place in
  isolation and all or none. Ex. Money transfer
  in a bank system
• Protection Maintenance
• System protection against hardware/software
  malfunction
• Backup and Recovery
• Security protection against unauthorized and
  malicious access
• User permissions

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DBMS (contd) Functions Maintenance

• As miniworld requirements change over time
  database needs to be maintained
• i.e., database evolves as the requirements
  change over time

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Database System

• Database and the DBMS software together are
  called a Database System

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More database terminology

• Entity (entity type)
• Represents a real world object or a concept
• Entity Set
• Collection of entities of a particular entity
  type
• Attribute
• Property of an entity
• Key
• An attribute or collection of attributes that
  uniquely identify an entity in an entity set
• Relationship
• Represents an association between entities (e.g.
  is-a)

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Example University System

• Organized as five files (tables)
• (note if the database is extended to several
  data locations, one table may correspond to
  several actual files)
• Note student information is missing in the next
  slide
• Student
• Name Student Number Class Major
• Smith 17 1
  CS

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Database as part of Information Systems (IT dept)
and - levels of abstraction

• Requirements Definition, Analysis, Design
• Conceptual Design
• Abstraction of the miniworld
• Entity Relationship (E-R) Diagrams
• Logical Design
• Implemented as a data model (e.g. relational data
  model)
• Physical Design
• Specification of storage and access of the
  database

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File processing vs. Database Approach

• File processing
• Each user defines and implements the files needed
  for their own application
• Data definition is typically part of the
  application program
• No sharing
• Redundancy (duplicate information - possibly
  inconsistent)

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File processing vs. Database Approach

• Database approach
• Single repository, many applications
• Self-describing nature of a database system
• Meta-data Description of the data and the
  constraints on that data are stored in data
  catalogs
• General purpose DBMS software can execute against
  any database table
• Data abstraction
• Program-data independence (structure of the data
  is separated from applications)
• Program-operation Independence (OO related)
  Interface/Implementation

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File processing vs. Database Approach(contd)

• Data Model
• Type of data abstraction that is used to provide
  conceptual representation
• A DBMS provides users with conceptual
  representation which hides storage and
  implementation details from the users

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File processing vs. Database Approach(contd)

• Multiple views of the data
• May contain virtual data (e.g., age based on DOB)
• Sharing of data and multi-user transaction
  processing
• Concurrency control
• e.g., in Online Transaction Processing (OLTP)
• Transaction
• Isolation
• Atomicity

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Database Catalog Example Self Describing Nature
of a DB System
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Example Internal Storage Format Data
Abstraction (e.g., consider request to access
name)
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Example Multiple Views
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Database Users (Actors on the Scene)

• Database Administrators
• Database Designers
• End Users (interested in the data itself)
• Casual End Users (occasional, e.g., managers)
• Naïve or parametric end users (more frequent
  users)
• canned transactions (e.g., bank tellers)
• Sophisticated end users (e.g. engineers,
  scientists)
• Standalone users (maintain personal databases
  using ready made programs)
• System Analysts and Application Programmers
  (Software Engineers or Developers)

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Workers Behind the Scene

• Associated with design, development, and
  operation of DBMS software and system environment
• Not typically interested in the actual data
• DBMS system designers and implementers
• Very complex software system
• Tool developers (e.g., performance monitoring)
• Operators and maintenance personnel (system
  administrators)

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Advantages of Using the DBMS Approach

• Controlling Redundancy
• Duplication of effort, wasted storage space,
  inconsistent data
• Controlled/Uncontrolled Redundancy
• Restricting Unauthorized Access
• Security Authorization Subsystem
• Providing Persistent Storage for Program Objects
  (for OO systems)
• Providing Storage Structures for Efficient Query
  Processing
• e.g., indices, buffering (from disk),
  optimization
• Part of physical database design and tuning

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Example Redundant Storage
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Advantages of Using the DBMS Approach(contd)

• Providing Backup and Recovery
• Providing Multiple User Interfaces
• e.g., forms style, GUI, command line
• Representing Complex Relationships among data
  (for efficient storage and retrieval)
• Enforcing Integrity Constraints
• Constraints are derived from the semantics of
  data
• Business rules
• Inherent rules of the data model
• Permitting Inferencing and Actions Using Rules
• Deductive database systems
• Triggers, stored procedures
• Active Database Systems

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Additional Implications of Using the Database
Approach

• Potential for Enforcing Standards
• Among database users
• Names/formats of data elements
• Reduced Application Development Time
• Flexibility (maintenance)
• Availability of Up-to-Date Information
• Economies of Scale
• Distributed Environments, Replication etc.

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History of Database Applications

• Hierarchical and Network Systems
• Intermixing of conceptual relationships with the
  physical storage and placement of records on disk
• Efficient access for original queries
  transactions
• New queries/transactions?
• Programming language interfaces
• Relational Databases
• Separate physical storage of data from its
  conceptual representation
• High level query language interface
• Object-Oriented Applications
• Object-Oriented Databases (OODB)
• Interchanging Data on the Web for E-commerce

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History of Database Applications (contd)

• Extending Database Capabilities for New
  Applications. examples
• Scientific
• Images
• Video
• Data mining
• Spatial
• Time series
• Databases vs Information Retrieval (IR)

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When Not to Use a DBMS

• Overhead costs
• High initial investment in hardware, software,
  and training
• Providing security, concurrency control etc.
• Simple, well-defined DB applications not expected
  to change
• Stringent, real-time requirements that cannot be
  met by DBMS
• No multiple-user access to data