Overview of Database Systems: Basic Concepts and Definitions

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Overview of Database Systems Basic Concepts and
Definitions
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The Database Environment
Strategic Databases
Decision support systems
Database Management System (DBMS)
Management Databases
Management information systems
Transaction processing systems
Transaction Databases
Information Resources Management
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Steps Involved in Converting Data to Information
DATA
INFORMATION
DISTRIBUTION
ACQUISITION
RETRIEVAL
STORAGE
MANIPULATION
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What is a database?

• A database is an electronic collection of texts,
  numeric values, graphs, or images which are
  systematically processed and stored in computers.
• A database is a structure that can house
  information about multiple types of entities, as
  well as relationships among the entities.

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What are entities, attributes and relationships?

• An entity is really just like a noun it is a
  person, place or thing. It is represented as a
  record in a database.
• An attribute is a property of an entity. It is
  represented as a field in a database record.
• A relationship is an association between
  entities. It is represented using a common field
  in a set of records.

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Types of Databases

• Bibliographic - each record is a reference or
  citation (may also include a summary or abstract)
  to a publication, magazine or journal article,
  news story, patent, conference paper, etc.
• Directory - each record gives factual information
  about companies, organizations, products, etc.
• Numeric - each record is a table of statistical
  data, often with text added.
• Full-text - each record include the complete text
  of magazine articles, newswire stories,
  encyclodepias, etc.
• Multimedia - each record may contain text,
  graphics, video and sound

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Entities, Attributes and Relationships
attributes

• ID Number
• Name
• Address
• Salary

Employee
relationship
entities
works
attributes

• Dept Code
• Name
• Location

Department
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Bibliographic record
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Directory record
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Fulltext record
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Numeric record
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Muti-media database example record
Multimedia record
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Database Management System

• A database management system, or DBMS, at its
  simplest is a software product through which
  users interact with a database.
• The actual manipulation of the underlying
  database structure and its content is handled by
  the DBMS.

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Functions of a Database Management System

• data storage, retrieval and update
• a user-accessible catalog or data dictionary
• transaction support (updating)
• concurrency control services (multiple updating)
• recovery services
• authorization services
• support for data communication and networking

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Schematic Diagram of A DBMS
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Advantages of Database Approach

• minimal data redundancy
• consistency of data
• integration of data
• sharing of data
• enforcement of standards
• ease of application development
• uniform security, privacy and integrity controls

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Disadvantages of the Database Approach

• size
• complexity
• cost
• additional hardware requirements
• higher impact of a failure
• recovery more difficult
• new, specialized personnel

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Stages of Database Development

• Planning
• Analysis and Design
• Implementation/Programming
• Operation and Maintenance
• Growth and Change

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Analysis and Design

• defining content, scope and users
• defining output requirements - e.g. screen and
  printed reports
• defining database record structures (i.e. in
  terms of attributes, entities and relationships)
• defining data entry screens
• defining user-interface

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Implementation

• selecting the appropriate DBMS software package
• creating database structure (i.e. records,
  fields, relationships, constraints, indexes,
  etc...)
• creating data entry screens
• creating report and display formats
• developing the application user-interface

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Operation and Maintenance

• entering and editing records
• retrieving records using queries and reports
• back-up and recovery

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Stages in a Database System Life Cycle
Planning
Growth and Change
Requirements formulation and analysis
Operation and Maintenance
Design
Implemen- tation
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Tips on Compiling a Database

• adopt standards
• design for network access

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Basic Definitions

• Database A collection of related data.
• Data Known facts that can be recorded and have
  an implicit meaning.
• Mini-world Some part of the real world about
  which data is stored in a database. For
  example, consider student names, student
  grades and transcripts at a university.

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Basic Definitions (contd.)

• Database Management System (DBMS) A software
  package/ system to facilitate the creation and
  maintenance of a computerized database. It
  defines (data types, structures, constraints)
  construct (storing data on some storage medium
  controlled by DBMS) and manipulate (querying,
  update, report generation) databases for various
  applications.
• Database System The DBMS software together with
  the data itself. Sometimes, the applications are
  also included.

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Example of a Database - Conceptual Data Model

• Mini-world for the example Part of a UNIVERSITY
  environment
• Some mini-world entities (Data elements)
• - STUDENTs
• - COURSEs
• - SECTIONs (of COURSEs)
• - (academic) DEPARTMENTs
• - INSTRUCTORs

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Example of a Database - Conceptual Data Model
(contd.)

• Some 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

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File Processing and DBMS

• File Systems
• - Store data over long periods of time
• - Store large amount of data
• Limitations
• - No guarantee that data is not lost if not
  backed up
• - No support to query languages
• No efficient access to data items unless the
  location
• is known

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File Processing and DBMS (contd.)

• - Application depends on the data definitions
  (structures)
• Change to data definition will affect the
  application
• programs
• - Single view of the data
• - Separate files for each application
• - Limited control to multiple accesses
• - Data viewed as physically stored

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Main Characteristics of Database Technology

• Self-contained nature of a database system
• A DBMS catalog stores the description
  (structure, type, storage format of each
  entities) of the database. The description is
  called meta-data). This allows the DBMS software
  to work with different databases.
• Insulation between programs and data
• Called program-data independence. Allows changing
  data storage structures and operations without
  having to change the DBMS access programs.

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Main Characteristics of Database Technology
(contd.)

• Data Abstraction
• A data model is used to hide storage details and
  present the users with a conceptual view of the
  database does not include how data is stored and
  how the operations are implemented.
• Support of multiple views of the data
• Each user may see a different view of the
  database, which describes only the data of
  interest to that user.
• Sharing of Data and Multiple users

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Main Characteristics of Database Technology
(contd.)

• DBA Database Administrator
• Responsible for authorizing access to the
  database, coordinating, monitoring its use,
  acquiring hardware, software needed
• Database designers
• responsible for identifying the data to be
  stored, storage structure to represent
  and store data. This is done by a
  team of professionals in consultation
  with users, and
  applications needed.

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Additional Benefits of Database Technology

• Controlling redundancy in data storage and in
  development and maintenance efforts
• Sharing of data among multiple users.
• Restricting unauthorized access to data.
• Providing multiple interfaces to different
  classes of users.
• Representing complex relationships among data.
• Enforcing integrity constraints on the
  database.
• Providing backup and recovery services.

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Additional Benefits of Database
Technology (contd.)

• Providing backup and recovery services.
• Potential for enforcing standards.
• Flexibility to change data structures.
• Reduced application development time.
• Availability of up-to-date information.
• Economies of scale.

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When not to use a DBMS

• Main inhibitors (costs) of using a DBMS
• - High initial investment and possible need for
  additional hardware.
• Overhead for providing generality, security,
  recovery, integrity, and
  concurrency control.
• When a DBMS may be unnecessary
• If the database and applications are simple, well
  defined,
• and not expected to change.

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When not to use a DBMS (contd.)

• If there are stringent real-time requirements
  that may
• not be met because of DBMS overhead.
• If access to data by multiple users is not
  required.
• When no DBMS may suffice
• If the database system is not able to handle the
  complexity of data because of
  modeling limitations
• If the database users need special operations not
  supported by the DBMS.