The document discusses database systems and Entity-Relationship (E-R) modeling. It defines various symbols and concepts in E-R diagramming such as entity types, attributes, relationships and cardinalities. It also outlines the process of designing a database schema including requirements analysis, conceptual design, logical design and physical design. Specialization, generalization and other enhanced E-R modeling features are presented with examples. Finally, it provides a brief history of database systems from the 1950s to the present.

1. Subject Name Code Credit Hours
Database System COMP 219 3
Chapter VI

2. Subject Name Code Credit Hours
Database System COMP 219 3
E-R Diagram
• Symbol Description
Entity Type
Attribute
Key Attribute

3. Subject Name Code Credit Hours
Database System COMP 219 3
E-R Diagram
Symbol Description
Composite Attribute
Multivalued attribute
Attribute

4. Subject Name Code Credit Hours
Database System COMP 219 3
E-R Diagram
Symbol Description
Derived Attribute
Relationship

5. Subject Name Code Credit Hours
Database System COMP 219 3
E-R Diagram
• Symbol Description
Identifying Relationship
Weak Entity Type

6. Subject Name Code Credit Hours
Database System COMP 219 3
E-R Diagram
• Symbol Description
E1 E2R
Total participation of E2 in R &
Partial Participation of E1 in R
E1 E2R
1 1
Cardinality Ratio
E2R
Min,max
Structural constraints
(min,max) on participation of
Environmental in R

7. Subject Name Code Credit Hours
Database System COMP 219 3
Recursive Relationship
• If the same entity type partcipates in a
relationship more than once in different roles.
• E.g.. Employee
Supervising
Supervisor
Supervise

8. Subject Name Code Credit Hours
Database System COMP 219 3
Design of an E-R Database Schema
The steps involved in designing an E-R database schema are,
• Identify entity types and their entity sets.
• List out the attributes of each entity type.
• Relate several entities by specifyiing some relationship that
exists among them.
• Specify some attributes of relation if any.
• Specify Generalization and specialization any exists.
• Specify Aggregation (global) if any used.

9. Subject Name Code Credit Hours
Database System COMP 219 3
Design Process:
• The main phases involved in designing a ER db schema is shown below,
Mini world
Requirements collection & Analysis
Data Requirements
Conceptual Design
Conceptual schema
Logical Design
Physical design
Logical schema
Internal Schema
Transaction
implementation
Functional Requirements
Functional Analysis
High level Transaction
specification
Application program
Design
App.pgms
DBMS
Independen
t
DBMS
Specific

10. Subject Name Code Credit Hours
Database System COMP 219 3
Requirements collection & Analysis
• The db designers interview db users to understand & document their
requirements.
• They find out data requirements (what data are stored in the db).
Conceptual Design:
• Once the requirements are documented , the next step is to create
conceptual schema which carried out in conceptual design Phase.
• It describes the structure of a db in the form of entity type, relationship
among them & constraints.

11. Subject Name Code Credit Hours
Database System COMP 219 3
Logical Design
• The actual implementation of the db is carried out using DBMS.
Physical Design
 The last phase is the internal storage structures, indexes,
access paths, and file organizations for the db files are
specified.
 In parallel with these activities, Application programs are
designed and implemented as db transactions.

12. Subject Name Code Credit Hours
Database System COMP 219 3
EER Model- Enhanced or Extended E-R model
• Using E-R model only the basic features of a db.
• Some enhanced features such as Specialization, Generalization, Union &
aggregation can be shown using EER model.
A. SPECIALIZATION:
The process of designating sub grouping within an
entity set..

13. Subject Name Code Credit Hours
Database System COMP 219 3
E.g…..
Employee
IS A
Secretary Technician Manager
eid ename eaddr Job
Typing speed
Mgrid

14. Subject Name Code Credit Hours
Database System COMP 219 3It is also represented as
Employee
eid ename eaddr Job
d
Secretary Technician Manager
d
Job Type
Salary Type
Hourly Regular
Defining attribute
Sub classes

15. Subject Name Code Credit Hours
Database System COMP 219 3
Generalization
•The process of defining a
generalized entity type
from the given entity types.

16. Subject Name Code Credit Hours
Database System COMP 219 3E.g…
CAR TRUCK
PriceMax speed
Vehicle ID No. of seats Vehicle ID
Price
No. Of Axles
Tonnage

17. Subject Name Code Credit Hours
Database System COMP 219 3
Vehicle
Vehicle ID
Price
d
CAR
TRUCK
Max speed
No. of seats Tonnage
No. Of Axles

18. Subject Name Code Credit Hours
Database System COMP 219 3
History of Database Systems
• 1950s and early 1960s:
– Data processing using magnetic tapes for storage
• Tapes provide only sequential access
– Punched cards for input
• Late 1960s and 1970s:
– Hard disks allow direct access to data
– Network and hierarchical data models in widespread use
– Ted Codd defines the relational data model
• Would win the ACM Turing Award for this work
• IBM Research begins System R prototype
• UC Berkeley begins Ingres prototype
– High-performance (for the era) transaction processing

19. Subject Name Code Credit Hours
Database System COMP 219 3
History (cont.)
• 1980s:
– Research relational prototypes evolve into commercial systems
• SQL becomes industrial standard
– Parallel and distributed database systems
– Object-oriented database systems
• 1990s:
– Large decision support and data-mining applications
– Large multi-terabyte data warehouses
– Emergence of Web commerce
• 2000s:
– XML and XQuery standards
– Automated database administration