This document discusses the database design process. It describes the design phases including initial requirements gathering, conceptual design, logical design, and physical design. It also covers design alternatives and avoiding redundancy and incompleteness. The main body explains the entity-relationship model including entity sets, relationship sets, attributes, keys, and extended features like specialization, generalization and inheritance. It concludes with discussing the unified modeling language and other database design aspects like constraints, requirements, and authorization.

1.  Paper Name – Database System
 Staff Name – Ms. S. Jamuna M.Sc.,
M.phil.,
 Class – II Year
 Semester – IV
 Unit – IV
 Topic – Entity-Relationship Model

3. Design Process:
 In Database the need of the users
play a central role in the design
process.
 It is classified into categories:
* Design Phases
* Design Alternatives

4. Design Phases:
 It may be feasible for a database
designer who understands the
application requirements directly on
the relation.
 Initial Phases: Database design is to
characterize fully the data need of the
prospective database user.

5. Design Phases(cont..):
 Next , the designer choose a data
model and applying the concepts of
the chosen model is refer to
Conceptual-design phase.
 The final two design phases:
1) Logical-design phase
2) Physical-design phase

6. Design Alternatives:
 A major part of the database design
process is deciding how to represent
in the design the various types of
“things” like, people, places etc.
 In designing a database schema,
avoid two major pitfalls:
@ Redundancy
@ Incompleteness

7. Entity-Relationship Model:
 The entity-relationship data model was
developed to allowing specification of an
enterprise structure.
 It is very useful in mapping and
interactions of real-world enterprises.
 The E-R model divided into three basic
concepts:
1, Entity set
2, Relationship set
3, Attributes

8. E-R model (cont..)
 Entity set: An entity is a ‘things’ or
‘object’. Ex: pen. And entity set is a
set of entities ex: pen box.
 Relationship set: Relationship is an
association among several entities. A
relationship set is a set of
relationships among the same type.

9. E-R model (cont..)
 Attributes: An entity is represented
by a set of attributes. Attribute are
descriptive properties possessed by
each member of an entity set.
 Attributes types:
% Simple and Composite
% Single-value and Multivalued
% Derived

10. Keys:
 Keys help to identify relationships
uniquely and thus differentiate the
relationships from each other.
 Types of keys:
* Primary Key
* Candidate Key
* Super Key
* Foreign Key

11. Extended E-R Features:
 The extended E-R features are:
 Specialization
 Generalization
 Higher and Lower-level entity set
 Attribute inheritance
 Aggregation

12. Extended E-R Features(cont..)
 Specialization: The process of
designating subgrouping within an
entity set.
 Generalization: Which is a
containment relationship that exists
between a higher-level entity set and
one or ore lower-level entity set.
 Attribute inheritance: A crucial
property of the higher and lower-level
entities created by specialization and
generalization is attribute inheritance.

13. Extended E-R model(cont..)
 Higher-level entity set;
* Total generalization and
specialization.
* Partial generalization and
specialization.
 Lower-level entity set:
* Condition-defined
* User-defined
* Disjoint
* Overlapping

15. The Unified Modeling
language(UML)
 The UML is a standard developed
under the auspices of the Object
Management Group for creating
various component of software
system.
 Some parts of UML:
& class diagram
& Use case diagram
& Activity diagram
& Implement diagram

16. Other Aspect of Database
Design
 Data Constraints and Relation
Database Design
 Usage Requirements: Queries,
Performance
 Authorization Requirements
 Data flow and work flow