Lecture Two Instructor: Fundamentals of Database Systems Course

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Fundamentals of Database Systems
Zahraa almayali 2022-2021 1
Lecture Two
Instructor: Zahraa Yahya AL Mayali
Fundamentals of Database
Systems Course

2
Characteristics of the Database Approach
Traditional file processing
Each user defines and implements the files needed for a specific
software application
Database approach
Single repository maintains data that is defined once and then
accessed by various users
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Characteristics of the Database Approach
(cont'd.)
Main characteristics of database approach
Self-describing nature of a database system
Insulation between programs and data, and
data abstraction
Support of multiple views of the data
Sharing of data and multiuser transaction
processing
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Self-Describing Nature of a Database
System
Database system contains complete definition of structure
and constraints
Meta-data
Describes structure of the database
Database catalog used by:
DBMS software
Database users who need information about database structure
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Insulation Between Programs and Data
Program-data independence
Structure of data files is stored in DBMS catalog separately from
access programs
Program-operation independence
Operations specified in two parts:
•Interface includes operation name and data types of its arguments
•Implementation can be changed without affecting the interface
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Data abstraction
Allows program-data independence and
program-operation independence
Conceptual representation of data
Does not include details of how data is stored
or how operations are implemented
Data model
Type of data abstraction used to provide
conceptual representation
Data Abstraction
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Support of Multiple Views of the Data
View
Subset of the database
Contains virtual data derived from the database files but is not
explicitly stored
Multiuser DBMS
Users have a variety of distinct applications
Must provide facilities for defining multiple views
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Sharing of Data and Multiuser Transaction
Processing
Allow multiple users to access the database at the same
time
Concurrency control software
Ensure that several users trying to update the same data do
so in a controlled manner
•Result of the updates is correct
Online transaction processing (OLTP) application
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Sharing of Data and Multiuser Transaction
Processing (cont'd.)
Transaction
Central to many database applications
Executing program or process that includes one or more database
Isolation property
•Each transaction appears to execute in isolation from other transactions
Atomicity property
•Either all the database operations in a transaction are executed or none
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Actors on the Scene
Database administrators (DBA) are responsible for:
Authorizing access to the database
Coordinating and monitoring its use
Acquiring software and hardware resources
Database designers are responsible for:
Identifying the data to be stored
Choosing appropriate structures to represent and store this data
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Actors on the Scene (cont'd.)
System analysts
Determine requirements of end users
Application programmers
Implement these specifications as programs
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Actors on the Scene (cont'd.)
End users
People whose jobs require access to the database
Types
•Casual end users
•Naive or parametric end users
•Sophisticated end users
•Standalone users
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A typical DBMS provides multiple facilities to access a database.
Naive end users need to learn very little about the facilities provided by
the DBMS; they simply have to understand the user interfaces of the
standard transactions designed and implemented for their use.
Casual users learn only a few facilities that they may use repeatedly.
Sophisticated users try to learn most of the DBMS facilities in order to
achieve their complex
requirements.
Standalone users typically become very proficient in using a specific
software package.
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DBMS system designers and implementers
Design and implement the DBMS modules and interfaces
as a software package
Tool developers
Design and implement tools
Operators and maintenance personnel
Responsible for running and maintenance of hardware and
software environment for database system
Workers behind the Scene
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Advantages of Using the DBMS Approach
Controlling redundancy
Data normalization
Denormalization
•Sometimes necessary to use controlled redundancy to improve the
performance of queries
Restricting unauthorized access
Security and authorization subsystem
Privileged software
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Advantages of Using the DBMS Approach
(cont'd.)
Providing persistent storage for program objects
Complex object in C++ can be stored permanently in an object-
oriented DBMS
Impedance mismatch problem
•Object-oriented database systems typically offer data structure
compatibility
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Providing backup and recovery
Backup and recovery subsystem of the DBMS is responsible
for recovery
Providing multiple user interfaces
Graphical user interfaces (GUIs)
Representing complex relationships among data
May include numerous varieties of data that are interrelated in
many ways
Advantages of Using the DBMS
Approach (cont'd.)
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Advantages of Using the DBMS Approach
(cont'd.)
Enforcing integrity constraints
Referential integrity constraint
•Every section record must be related to a course record
Key or uniqueness constraint
•Every course record must have a unique value for Course_number
Business rules
Inherent rules of the data model
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Advantages of Using the DBMS Approach
(cont'd.)
Permitting inferencing and actions using rules
Deductive database systems
•Provide capabilities for defining deduction rules
•Inferencing new information from the stored database facts
Trigger
•Rule activated by updates to the table
Stored procedures
•More involved procedures to enforce rules
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Advantages of Using the DBMS
Approach (cont'd.)
Additional implications of using the
database approach
Reduced application development time
Flexibility
Availability of up-to-date information
Economies of scale
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A Brief History of Database Applications
Early database applications using hierarchical and network
systems
Large numbers of records of similar structure
Providing data abstraction and application flexibility with
relational databases
Separates physical storage of data from its conceptual
representation
Provides a mathematical foundation for data representation and
querying
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A Brief History of Database Applications
(cont'd.)
Object-oriented applications and the need for more complex
databases
Used in specialized applications: engineering design, multimedia
publishing, and manufacturing systems
Interchanging data on the Web for e-commerce using XML
Extended markup language (XML) primary standard for
interchanging data among various types of databases and Web
pages
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A Brief History of Database Applications
(cont'd.)
Extending database capabilities for new applications
Extensions to better support specialized requirements for
applications
Enterprise resource planning (ERP)
Customer relationship management (CRM)
Databases versus information retrieval
Information retrieval (IR)
•Deals with books, manuscripts, and various forms of library-based
articles
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Review Questions
1.1. Define the following terms: data, database, DBMS, database system, database catalog, program-
data independence, user view, DBA, end user, canned transaction, deductive database system,
persistent object, meta-data, and transaction-processing application.
1.2. What four main types of actions involve databases? Briefly discuss each.
1.3. Discuss the main characteristics of the database approach and how it differs from traditional file
systems.
1.4. What are the responsibilities of the DBA and the database designers?
1.5. What are the different types of database end users? Discuss the main activities of each.
1.6. Discuss the capabilities that should be provided by a DBMS.
1.7. Discuss the differences between database systems and information retrieval systems.
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