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INF 280 Database Systems
BASIC CONCEPTS
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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Typical software application
Business Logic
INF 280
I
n
t
e
r
f
a
c
e
D. Christozov / G.Tuparov
Transforming
interface into
data request
Query (SQL)
Data Processing
Transforming
datasets into
reports/forms
Datasets
INF 280 Database Systems:
Basic Concepts
Database
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Basic Concepts - Topics
1. A database as a collection of related data
2. Database and Database Management System
3. Characteristics and advantages of DB
approach
4. DB users
5. DB Architecture
6. DBMS Architecture
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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DB as a collection of related data (1)
• Data: facts that can be recorded and that have implicit
meaning.
• Database implicit properties:
– A database represents some aspect of the real world,
sometimes called the miniworld or the Universe of
Discourse (UoD).
– A database is a logically coherent collection of data
with some inherent meaning.
– A database is designed, built, and populated with data
for a specific purpose. It has an intended groups of
users and some preconceived applications in which
these users are interested.
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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DB as a collection of related data (2)
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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Basic characteristics
1. Self-Describing Nature of a Database System
2. Insulation between Programs and Data, Data
Abstraction
3. Support of Multiple Views of the Data
4. Sharing of Data and Multiuser Transaction
Processing
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Basic Concepts
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Basic characteristics (1)
Self-Describing Nature of a Database System
• System catalogue contains information about the
structure of each file, the type and storage format of
each data item, and various constraints on the data.
The information stored in the catalogue is called
meta-data, and it describes the structure of the
primary database.
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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Basic characteristics (2)
Insulation between Programs and Data, and Data
Abstraction
• The characteristic that allows program-data
independence and program-operation independence is
called data abstraction.
• A DBMS provides users with a conceptual
representation of data that does not include many of
the details of how the data is stored or how the
operations are implemented. Data model (or logical
data model) is a type of data abstraction that is used to
provide this conceptual representation. Data model
hides storage and implementation details.
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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Basic characteristics (3)
Support of Multiple Views of the Data
• A view may be a subset of the database or it may
contain virtual data that is derived from the database
files but is not explicitly stored.
• Different categories of users need different views on
the database.
• One user may need to solve different problems with
database and for every problem may need different
view on the data.
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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Basic characteristics (4)
Sharing of Data and Multiuser Transaction
Processing
• Multiple users may need to access database
simultaneously.
• The DBMS must include concurrency control
software to ensure that several users trying to
update the same data do so in a controlled manner
so that the result of the updates is correct.
• On-line transaction processing (OLTP) applications.
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Basic Concepts
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Advantages of Using DBMS
•
•
•
•
•
•
•
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Controlling Redundancy (reducing)
Preserving Data Integrity
Restricting Unauthorized Access
Providing Persistent Storage for Program Objects
and Data Structures (Object-Oriented DB)
Permitting Inferencing and Actions Using Rules
Providing Multiple User Interfaces
Representing Complex Relationships Among Data
Providing Backup and Recovery
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Redundant Data
Id#
Name
Address
Code
000101
Ivan Ivanov
Scapto 1
COS480
DB System
3
000101
Ivan Ivanov
Scapto 1
COS 221
FDS
000101
Ivan Ivanov
Scapto 1
AUB 102
000102
Georgi Georgiev
Scapto 2
000102
Georgi Georgiev
Scapto 2
Student’s
information
D. Christozov / G.Tuparov
Title
Cr.
Instructor
Section
Grade
Christozov
A
B-
3
Christozov
B
B+
Writing
3
Colman
C
D+
COS 480
DB System
3
Christozov
A
B+
AUB 102
Writing
3
Colman
C
C+
Course
information
INF 280 Database Systems:
Basic Concepts
Grade
information
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Integrity
Grades
Id#
Name
Address
Code
Title
Cr.
Instructor
Section
Grade
000101
Ivan Ivanov
Scapto 1
COS480
DB System
3
Christozov
A
B-
000101
Ivan Ivanov
Scapto 1
COS 221
FDS
3
Christozov
B
B+
000101
Ivan Ivanov
Scapto 1
AUB 102
Writing
3
Colman
C
D+
000102
Georgi Georgiev
Scapto 2
COS 480
DB System
3
Christozov
A
B+
000102
Georgi Georgiev
Scapto 2
AUB 102
Writing
3
Colman
C
C+
missing
Faculty
Family Name
Given Name
Title
Office
Bonev
Stoyan
Assoc. Professor
221
Colman
Mark
Professor
231
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Basic Concepts
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Actors on the Scene
• DB Administrators
• DB Designers
• End Users:
– Casual
– Naive (parametric)
– Sophisticated
– Stand-alone
– System Analysts and Application Programmers
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Basic Concepts
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Actors Behind the Scene
• DBMS Systems designers and implementers
• Tools developers
• Operators and Maintenance personnel
D. Christozov / G.Tuparov
INF 280 Database Systems:
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DB History
Database Systems:
the success story of Computer Science
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•
•
•
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Early applications: use of File Systems
1960s: Hierarchical and Network DB models
Late 1970s: Codd’s Relational Model
Late 1980s: OODB -> R-OO DB
1990s: SQL standards, WWW, E-Commerce
Spatial DB, Data Warehouses, Data Mining
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DB Model
Data Model:collection of concepts that can be used to
describe the structure of a database
Structure: data types; relationships; constraints
Operation: retrieve, insert, delete, modify
user-defined operations
Behavior: dynamic
Object-Oriented Models incorporate both structure and
behavior
In “classical” models (hierarchical, network or
relational) behavior is limited to generic operations.
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DB Model: Categories of Data Models
High-level – conceptual: How users perceive data.
Low-level – physical:
How data is actually stored on
computer.
Representational
Close to the way users
– logical:
understand data, but allow direct
interpretation by given DBMS
Database schema:
Description of database model
Diagram
Schema  Instance  State
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DB and DBMS
• A database management system (DBMS) is a
collection of programs that enables users to
create and maintain a database.
• The DBMS is a general-purpose software
system that facilitates the processes of
– defining,
– constructing, and
– manipulating
databases for various applications.
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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DBMS
• DBMS supports the following categories of
languages:
– Data definition language (DDL).
– Storage definition language (SDL)
– View definition language (VDL)
– Data manipulation language (DML), including
querying language
• Note: In current DBMSs, these types of
languages are not considered distinct
languages
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Basic Concepts
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DBMS Components
DB designers
DB administrators
Sophisticate Users
Naïve Users
Query compiler
DML compiler
DDL interpreter
System catalogue
Run-time processor
Boundaries of DBMS
Data manager
Concurrency control,
recovery, backup
subsystems
Recorded DB
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DBMS Architecture
• The Three-Schema Architecture
1. The internal level (internal schema), describes
the physical storage structure of the database.
2. The conceptual level (conceptual schema),
describes the structure of the whole database for
a community of users.
3. The external or view level includes a number of
external schemas or user views.
• Data Independence
1. Logical data independence.
2. Physical data independence
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The Three-Schema Architecture
Categories of
Users
External Schemas
Logical Data
Independence
Logical Schema
Physical Schema
Data Files
Master Files
D. Christozov / G.Tuparov
Indexes
INF 280 Database Systems:
Basic Concepts
Physical Data
Independence
Meta Data
System Catalog
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Database System Utilities
1.
2.
3.
4.
Loading
Backup
File reorganization
Performance monitoring
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Basic Concepts
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Q&A
D. Christozov / G.Tuparov
INF 280 Database Systems:
Basic Concepts
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