Ch01-Introduction Databases and Database Users.ppt

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Copyright © 2007 Ramez Elmasri and Shamkant B. Navathe

Chapter 1
Introduction: Databases and
Database Users

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Outline
 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

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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 other applications
 First part of book focuses on traditional applications
 A number of recent applications are described later in the
book (for example, Chapters 24,26,28,29,30)

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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, student grades and transcripts at a
university.
 Database Management System (DBMS):
 A software package/ system to facilitate the creation and
maintenance of a computerized database.
 Database System:
 The DBMS software together with the data itself. Sometimes, the
applications are also included.

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Simplified database system environment

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Typical DBMS Functionality
 Define a particular database in terms of its data types,
structures, and constraints
 Construct or Load the initial database contents on a
secondary storage medium
 Manipulating the database:
 Retrieval: Querying, generating reports
 Modification: Insertions, deletions and updates to its content
 Accessing the database through Web applications
 Processing and Sharing by a set of concurrent users and
application programs – yet, keeping all data valid and
consistent

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Typical DBMS Functionality
 Other features:
 Protection or Security measures to prevent
unauthorized access
 “Active” processing to take internal actions on data
 Presentation and Visualization of data
 Maintaining the database and associated
programs over the lifetime of the database
application

Called database, software, and system
maintenance

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Example of a Database
(with a Conceptual Data Model)
 Mini-world for the example:
 Part of a UNIVERSITY environment.
 Some mini-world entities:
 STUDENTs
 COURSEs
 SECTIONs (of COURSEs)
 (academic) DEPARTMENTs
 INSTRUCTORs

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Example of a Database
(with a Conceptual Data Model)
 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
 Note: The above entities and relationships are typically
expressed in a conceptual data model, such as the
ENTITY-RELATIONSHIP data model (see Chapters 3, 4)

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Example of a simple database

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Main Characteristics of the Database
Approach
 Self-describing nature of a database system:
 A DBMS catalog stores the description of a particular
database (e.g. data structures, types, and constraints)
 The description is called meta-data.
 This allows the DBMS software to work with different
database applications.
 Insulation between programs and data:
 Called program-data independence.
 Allows changing data structures and storage organization
without having to change the DBMS access programs.

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Example of a simplified database catalog

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Approach (continued)
 Data Abstraction:
 A data model is used to hide storage details and
present the users with a conceptual view of the
database.
 Programs refer to the data model constructs rather
than data storage details
 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.

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 Sharing of data and multi-user transaction
processing:
 Allowing a set of concurrent users to retrieve from and to
update the database.
 Concurrency control within the DBMS guarantees that each
transaction is correctly executed or aborted
 Recovery subsystem ensures each completed transaction
has its effect permanently recorded in the database
 OLTP (Online Transaction Processing) is a major part of
database applications. This allows hundreds of concurrent
transactions to execute per second.

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Database Users
 Users may be divided into
 Those who actually use and control the database
content, and those who design, develop and
maintain database applications (called “Actors on
the Scene”), and
 Those who design and develop the DBMS
software and related tools, and the computer
systems operators (called “Workers Behind the
Scene”).

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Database Users
 Actors on the scene
 Database administrators:

Responsible for authorizing access to the database,
for coordinating and monitoring its use, acquiring
software and hardware resources, controlling its use
and monitoring efficiency of operations.
 Database Designers:

Responsible to define the content, the structure, the
constraints, and functions or transactions against
the database. They must communicate with the
end-users and understand their needs.

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Categories of End-users
 Actors on the scene (continued)
 End-users: They use the data for queries, reports
and some of them update the database content.
End-users can be categorized into:

Casual: access database occasionally when
needed

Naïve or Parametric: they make up a large section
of the end-user population.
 They use previously well-defined functions in the form of
“canned transactions” against the database.
 Examples are bank-tellers or reservation clerks who do
this activity for an entire shift of operations.

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Categories of End-users (continued)

Sophisticated:
 These include business analysts, scientists, engineers,
others thoroughly familiar with the system capabilities.
 Many use tools in the form of software packages that work
closely with the stored database.

Stand-alone:
 Mostly maintain personal databases using ready-to-use
packaged applications.
 An example is a tax program user that creates its own
internal database.
 Another example is a user that maintains an address book

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Advantages of Using the Database
Approach
 Controlling redundancy in data storage and in
development and maintenance efforts.
 Sharing of data among multiple users.
 Restricting unauthorized access to data.
 Providing persistent storage for program Objects
 In Object-oriented DBMSs – see Chapters 20-22
 Providing Storage Structures (e.g. indexes) for
efficient Query Processing

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Advantages of Using the Database
 Providing backup and recovery services.
 Providing multiple interfaces to different classes
of users.
 Representing complex relationships among data.
 Enforcing integrity constraints on the database.
 Drawing inferences and actions from the stored
data using deductive and active rules

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Additional Implications of Using the
Database Approach
 Potential for enforcing standards:
 This is very crucial for the success of database
applications in large organizations. Standards
refer to data item names, display formats, screens,
report structures, meta-data (description of data),
Web page layouts, etc.
 Reduced application development time:
 Incremental time to add each new application is
reduced.

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Additional Implications of Using the
Database Approach (continued)
 Flexibility to change data structures:

Database structure may evolve as new
requirements are defined.
 Availability of current information:
 Extremely important for on-line transaction
systems such as airline, hotel, car reservations.
 Economies of scale:

Wasteful overlap of resources and personnel can
be avoided by consolidating data and applications
across departments.

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Historical Development of Database
Technology
 Early Database Applications:
 The Hierarchical and Network Models were introduced in
mid 1960s and dominated during the seventies.
 A bulk of the worldwide database processing still occurs
using these models, particularly, the hierarchical model.
 Relational Model based Systems:
 Relational model was originally introduced in 1970, was
heavily researched and experimented within IBM Research
and several universities.
 Relational DBMS Products emerged in the early 1980s.

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Technology (continued)
 Object-oriented and emerging applications:
 Object-Oriented Database Management Systems
(OODBMSs) were introduced in late 1980s and early 1990s
to cater to the need of complex data processing in CAD and
other applications.

Their use has not taken off much.
 Many relational DBMSs have incorporated object database
concepts, leading to a new category called object-relational
DBMSs (ORDBMSs)
 Extended relational systems add further capabilities (e.g. for
multimedia data, XML, and other data types)

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Technology (continued)
 Data on the Web and E-commerce Applications:
 Web contains data in HTML (Hypertext markup
language) with links among pages.
 This has given rise to a new set of applications
and E-commerce is using new standards like XML
(eXtended Markup Language). (see Ch. 27).
 Script programming languages such as PHP and
JavaScript allow generation of dynamic Web
pages that are partially generated from a database
(see Ch. 26).

Also allow database updates through Web pages

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Extending Database Capabilities
 New functionality is being added to DBMSs in the following areas:
 Scientific Applications
 XML (eXtensible Markup Language)
 Image Storage and Management
 Audio and Video Data Management
 Data Warehousing and Data Mining
 Spatial Data Management
 Time Series and Historical Data Management
 The above gives rise to new research and development in
incorporating new data types, complex data structures, new
operations and storage and indexing schemes in database systems.

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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, concurrency
control, recovery, and integrity functions.
 When a DBMS may be unnecessary:
 If the database and applications are simple, well defined,
and not expected to change.
 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.

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When not to use a DBMS
 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.

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Summary
 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

Ch01-Introduction Databases and Database Users.ppt

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