Introduction: Databases and Database Users
Introduction: Databases and Database Users
Introduction: Databases and Database Users
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 20,21,22,23,24, 25 and 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.
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
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, keeping all data valid and consistent
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Typical DBMS Functionality
Other features:
Protection or Security :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
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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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Main Characteristics of the
Database 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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Main Characteristics of the
Database Approach (continued)
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.
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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
Approach (continued)
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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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 (GIS)
Time Series and Historical Data Management
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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
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