Transcript Course Introduction

Course Introduction
2nd
Ria Mae G. Corda
ITB322 (Lecture)
Semeseter, AY 2009 - 2010
Outline
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Introducing the database and related terms
A REAL LIFE example
The database approach
The database actors
Outline
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Behind the scene
The DBMS advantage
When NOT to use DBMS
Summary
Introducing the database and
related terms
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Traditional Database Applications
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Information is stored textually or numerically
Multimedia Database Applications
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Images, audio clips and video streams can be
stored
Geographic information systems
Data warehouses
Online analytical processing (OLAP)
Real-time/Active database technology
Introducing the database and
related terms
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Database
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Collection of related data
Data
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Known facts
Can be recorded
Have implicit meaning
Introducing the database and
related terms
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Properties of a database
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Represents some aspect of the real world
Logically coherent collection of data with inherent
meaning
Designed, built and populated for a specific
purpose
Introducing the database and
related terms
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A database may be maintained manually or it
may be computerized
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In this course we are only concerned about
computerized databases
A computerized database may be created an
manipulated using application programs or by a
database management system
Introducing the database and
related terms
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Database Management System (DBMS)
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A collection of programs that enables users to
create and maintain a database
A general-purpose software system that facilitates
the processes of defining, constructing,
manipulating, and sharing databases among
various users and applications
Introducing the database and
related terms
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Defining a database
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Involves specifying the data type, structures,
and constraints of the data to be stored in the
database.
The database definition is also stored in the
database
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Meta-data is the database catalog or dictionary
Introducing the database and
related terms
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Constructing the database
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The process of storing the data on some storage
medium controlled by the DBMS
Introducing the database and
related terms
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Manipulating a database
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Includes querying the database for information
retrieval, updating the database to reflect
changes in the real world, and generating
reports from the data.
Introducing the database and
related terms
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Sharing a database
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Allows multiple users and programs to access the
database simultaneously.
Introducing the database and
related terms
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Application program
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Accesses the database by sending queries or
requests for data to the DBMS
Introducing the database and
related terms
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Query
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Typically causes for some data to be retrieved.
Transaction
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Causes some data to be read and some data to
be written into the database.
Introducing the database and
related terms
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Protection
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System protection against hardware or software
malfunction,
Security protection against unauthorized or
malicious access.
Maintenance
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Allowing the system to evolve as requirements
change over time
Introducing the database and
related terms
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It is not necessary to use general-purpose
DBMS software to implement a computerized
database.
Database system
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The database and the DBMS software together
A REAL LIFE example
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The SCENARIO
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A UNIVERSITY database for maintaining
information concerning students, courses, and
grades in a university environment
Has five files: STUDENT, COURSE, SECTION,
GRADE_REPORT, PREREQUISITE
A REAL LIFE example
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Defining the database
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We must define the data types of each data
element in each record
A REAL LIFE example
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Constructing the database
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We store the data regarding each student,
course, section, grade report, and prerequisite
A REAL LIFE example
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Manipulating the database
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Involves querying and updating
Example: retrieving the transcript, changing
sections, creating a new course, etc
A REAL LIFE example
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Requirements definition and analysis
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Identifying business rules and needs
Conceptual design
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A model of the requirements to be able to
transform it into a database implementation
A REAL LIFE example
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Logical design
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Expression of the model in a DBMS software
implementation
Physical design
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Specifications for physical storage and access of
the database
The database approach
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File-processing system vs. database system
File Processing System
Database System
Each user defines and
implements the files
needed for the application
Each application is free to
name data elements
independently
A data repository is
defined once then
accessed by various users
The names and labels of
data are defined one
The database approach
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Self-describing nature of a database system
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The database system does not just contain the
database itself but even the database definition
called meta-data
Should work with any number of database
applications as long as the database definition is
available
The database approach
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Insulation between programs and data, and
data abstraction
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DBMS access programs do not require changing
all programs that access the database when a
structural change happens (program-data
independence)
The database approach
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Insulation between programs and data, and
data abstraction
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User application programs can operate on the
data by invoking operations regardless of how the
operation is implemented (program-operation
independence)
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Operation is a function or method made up of
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Interface which contains the name and parameters
– Implementation which defines the operation
The database approach
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Insulation between programs and data, and
data abstraction
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Data abstraction
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Characteristic that allows program-data independence
and program-operation independence
Data model is a type of data abstraction
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Hides storage and implementation details that are not of
interest to most database users
The database approach
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Support of multiple views of the data
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Although there is a single repository of data, only
a subset of this data may be made available to a
particular set of users
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A view is virtual data derived from the database but not
explicitly stored
The database approach
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Sharing of data and multi-user transaction
processing
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Transaction
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An executing program or process that includes one or
more database accesses such as reading or updating
the database
Needs to have concurrency control, isolation, and
atomicity
The database approach
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Sharing of data and multi-user transaction
processing
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Concurrency control
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Isolation
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Ensures that several users trying to update the same data do
so in a controlled manner
Ensures that each transaction appears to execute in isolation
from other transactions
Atomicity
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Ensures that either all the database operations in a transaction
are executed or none are.
The database actors
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Database administrators (DBA)
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A chief administrator to oversee and manage the
database, the DBMS, and other related software.
Responsible for:
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authorizing access to the database
coordinating and monitoring its use, and
acquiring software and hardware resources as needed.
Accountable for breach of security or poor system
response time.
The database actors
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Database designers
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Responsible for
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Identifying the data to be stored in the database
Choosing appropriate structures to represent and store
data
Communicating to prospective database users to
understand the requirements
Creating a design that fits user requirements
Final database design must be capable of
supporting the requirements of ALL user groups
The database actors
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End users
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Casual end users
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Occasionally access the database
May need different information every time
Use sophisticated query language to specify their
requests
Typically management level
The database actors
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End users
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Naïve or parametric end users
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Make up the sizeable portion of database end users
Constantly querying and updating the database
Use canned transaction
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Standard types of queries and updates
Examples: bank tellers, reservation clerks, cashiers
The database actors
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End users
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Sophisticated end users
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Engineers, scientists, business analysts
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Thoroughly familiarize themselves with the DBMS facilities
to implement their applications
The database actors
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End users
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Standalone users
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Maintain personal databases
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Uses ready-made program packages that provide easy-touse menu-based or graphics-cased interfaces.
The database actors
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End users
User
Level of DBMS expertise
Casual
Minimal
Naïve or parametric
Minimal
Sophisticated
Very high
Standalone
Proficient in using a
specific software package
The database actors
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System analysts and application
programmers
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System analyst
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Application programmer
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Determine the requirements of end users
Develop specifications for canned transactions that meet
these requirements
Implement the specifications as programs
Also tests, debugs, documents and maintains
Also known as software engineers/developers
Behind the scene
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Other personnel are associated with the
design, development, and operation of the
DBMS software itself and the system
environment surrounding it
They are instrumental in making the
database system available to end users but
do not use the database for their own
purpose
Behind the scene
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DBMS system designers and implementers
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Design and implement the DBMS modules and
interfaces as a software package
Ensures that the DBMS can interface with
operating systems and programming language
compilers
Behind the scene
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Tool developers
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Design and implement tools
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Tools are software packages that facilitate database
modeling and design, database system design, and
improved performance.
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Often purchased separately
Behind the scene
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Operators and maintenance personnel
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System administration personnel
Responsible for the actual running and
maintenance of hardware and software
environment for the database system
The DBMS Advantage
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Controlling redundancy
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Redundancy is storing the same data multiple
times which leads to
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Duplication of effort
Waste of storage space
Data inconsistency
Should allow controlled redundancy in some
cases
The DBMS Advantage
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Restricting unauthorized access
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A database system should have a security and
authorization subsystem
Only certain people can be given privilege to
access confidential data at different levels
The DBMS Advantage
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Providing persistent storage for program
objects
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Persistency
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Ability of data to survive even after the program is
terminated to enable later access of other programs.
The DBMS Advantage
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Providing storage structures for efficient
query processing
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Indexes
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Buffering module
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Data structures that allow efficient disk search
Provided by the DBMS to maintain parts of the database
in the main memory
Query processing and optimization module
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Enables the choosing of an efficient query execution
plan based on existing storage structures
The DBMS Advantage
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Providing backup and recovery
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The DBMS should have a recovery facility to
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Restore the database in a state before a system failure
occurred
Resume the transaction from the point where it was
interrupted
The DBMS Advantage
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Providing multiple user interfaces
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A DBMS should be able to provide:
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Query languages for casual users
Programming language interfaces for application
programmers
Forms and command codes for parametric users
Menu-driven interfaces and natural language interfaces
for standalone users
Graphical user interface (GUI) can be forms-style
or menu-style
The DBMS Advantage
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Representing complex relationships among
data
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The DBMS must have the capability to
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Represent complex relationships among the data
Define new relationships as they arise
Retrieve and update related data easily and efficiently
The DBMS Advantage
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Enforcing integrity constraints
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Integrity constraints
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Rules that must hold for the data
Example: data type, uniqueness of data
Some constraints can be specified to the DBMS
and automatically enforced
Others can be checked by the update programs
or the applications during data entry
The DBMS Advantage
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Permitting inferencing and actions using
rules
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Deductive database systems
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A DBMS which provides capabilities for defining
deduction rules for inferencing new information from the
stored database facts
Triggers
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A form of a rule activated by updates to the table, which
results to operations on other tables, sending messages,
etc.
The DBMS Advantage
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Permitting inferencing and actions using
rules
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Stored procedures
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Become a part of the overall database definition
Invoked when conditions are met
Active database systems
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Provide active rules that can automatically initiate
actions when certain events and conditions occur
The DBMS Advantage
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Some added advantages
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Potential for enforcing standards
Reduced application development time
Flexibility
Availability of up-to-date information
Economies of scale
When NOT to use DBMS
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Database overhead costs
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Initial investment in hardware, software, and
training
Generality for defining and processing data
Overhead for providing security, concurrency
control, recovery, and integrity functions
When NOT to use DBMS
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Circumstances where DBMS is not ideal
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Simple, well-defined database applications NOT
expected to change
Stringent, real-time requirements
No multiple-user access to data
When NOT to use DBMS
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Industries which do not use general-purpose
DBMS
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Computer-aided design (CAD) tools
Communication and switching systems
Geographical information systems (GIS)