DBMS OF DATA MODEL Deepika 2

Presentation prepration
 Guided By: . Presented By:
 C.L. Malviya sir . Deepika Yadav –B.Sc 5th sem.
 Sanjay shinde . Deepika rajput-B.Sc5th sem.
. Diksha Soniya-B.Sc5th sem.

Presentation on:
DBMS OF DATA MODEL

 DATA MODEL


 ‘ Data model are different models that can be used to design a
database. Design of database includes describing data, data
relationships, data semantics and consistency constrains. Various data
model have been proposed with different structure & abstractions.’

Object-based data model
Object-based logical models are used in describing data at the logical and
view levels.They are characterized by the fact that they provide fairly
flexible structuring capabilities and allow data constraints to be
specified explicitly.There are many different models and more are likely
to come. Several of the more widely known ones are-
1. The entity-relationship model
2.The object-oriented model
3. The semantic data model
4. The functional data model
In this book, We examine the entity-relationship model and the object-
oriented model as representatives of the class of the object-based
logical models.

1. The Entity-Relationship Data Model
 The entity-relationship (E-R) data models is based on a perception of a
real world that consists of a collection of basic objects, called entities
and of relationships among these objects. An entity is a ‘things’ or
‘object’ in the real world that is distinguishable form other objects.
Entities are described in a database by a set of attributes. A relationship
is an association among several entities. The set of all entities of the
same type, and the set of all relationships of the same type, respectively.

 In addition to entities and relationships, the E-R Model
represents certain constraints to which the contents of a database must
conform. One important constraint is mapping cardinalities, which
express the number of entities to which another entity can be
associated via a relationship set.

2. The Object-Oriented Data Model
 Like the E-R model , the object-oriented model is based on a collection
of objects. An object contains values stored in instance variables within
the object. An object also contains bodies of code that operate on the
object. These bodies of code are called methods.
 Object that contian
the same types of values and the same methods are grouped together
into classes. A class may be a type definition for objects. This
combination of data and methods comprising a type definition is
similar to a programming language abstract data type.

 The only way in which one object can access the data of another
object is by invoking a method of that other object. This action is called
sending a message to the object.

Record – Based Data Model
 Record-based logical models are used in describing data at the logical
and view levels. In contrest to object-based data models, they are used
both to specify the overall logical structure of the database and to
provide a higher-level description of the implementation .
 Record –based models are so named because the database is
structured in fixed-format records of several types.

 Typs of Record-based data model : 1. Relational Data Model
 2. Network Data Model
 3. Hiierarchical Data Model
 The three most widely accepted record-based data models are the
relational, network and hierarchical models.

 The relational model uses a collection of tables to represent both data
and the relationships among those data. Each table has multiple
columns and each column has a unique name . Figure 1.4 presents a
sample relational database comprising of two tables .
 Relational database are powerful
because they require few assumptions about how data is related or how
it will be extracted from the database . As a result, the same database
can be viewed in different ways. Another feature of relational systems is
that a single database can be spread across several tables. This differs
foem flat-file database, in which each database is self- contained in a
single table.

Relational Data Model

.Features of relational model.
 This model has the following fearures-
 1. All the data is represented in the form of table.
 2. Each attributes of a relation has distinct name.
 3. Tt eliminates the need to change application programs when a
change is made to the database.
 4. User need not know the exact physical structures to use the database.
 Advantages of relational model :
 1. Structural independence
 2. Conceptual simplicity
 3. Design,Implementation,Maintenance and Usage Ease
 4. Ad Hoc Query Capability

Disadvantage of relational model:
1. Hardware Overheads.
2. Ease of Design can lead to bad design.

2. Network Data Model
 Data in the network model are represented by collections of records
and relationships among data are represented by links, which can be
viewed as pointers. The records in the database are organized as
collections of arbitrary graphs.
 Figure presents a sample network database.

Features of Network Data Model
 Network model is has the following features-
 1. Data is represented by records and links.
 2. Relationship among the data is represented by links or pointers.
 3. All the records are organized in orbitaty form.
 4. The set can have more than one member record but only one owner
record.
 5. The set has one to many (1:M) relationship between the owner and
member record.

 Advantages of Network Data Model:
 1. Conceptual Simplicity
 2. Capability to handle more relationships types
 3. Ease to data access
 4. Data Intergrity
 5.Data Independence
 6. Database Standards
 Disadvantages of Network Data Model:
 1. System Complexity
 2. Absence of Structural Independence

 The hierarchical model is similar to the network model in the sense that
data and relationships among data represented by records and links,
respectively. It .differs form the network model in that the records are
organized as collections of tress rather than arbitrary graphs. one of the
first hierarchical database information Management System (IBM) was
developed jointly by North American Rockwell Company and
IBM.Hierarchical Database model is one of the oldest database models,
dating from late 1950s.
 Figure represents e sample hierarchical database.
.Hierarchical Data Model.

.Features of Hierarchical Model.
 Hierarchical model has the following features-
 1. It is very similar to network model except the records are organized
in tree form.
 2. Hierarchical is an ordered tree and is easy to understand.
 3. Again data is represented in the form of records.
 4. Similarly relationship among the data is represented by records or
links.
 5. At the root of the tree is the single parent, the parent can have none,
one or more children.

 Advantages of hierarchical data model :
 1. Simplicity
 2. Data security
 3. Data Integrity
 4. Efficiency
:
 Disadvantages of Hierarchical Data Model :
 1. Implementation complexity
 2.Database Management problems
 3. Lack of Structural Independence
 4. Programming Complexity
 5. Implementation Limitation

.Physical Data Model.
 Physical data models are used to describe data at the lowest level. In
contrast to logical data models, there are few physical data models in
use. Two of the widely known ones are the unifying model and the
frame memory model.
 Types of physical data model :
 1. Unifying Model
 2. Frame Memory Model

DBMS OF DATA MODEL Deepika 2

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