2. DATA MODELS INTRODUCTION
o A Data Model is a set of concepts that can be used to describe the structure
of data in a database.
o A database model shows the logical structure of a database, including the
relationships and constraints that, determine how data can be stored and
accessed.
o Data Models are used to support the development of information systems
by providing the definition and format of data to be involved in future
systems.
o The data model also gives an idea about possible alternatives to achieve
a targeted solution.
3. Types of Data Models
Hierarchical Model
Network Model
Relational Model
4. Hierarchical Model
This model is developed by IBM and the North American Rockwell Known
Information Management System. This is the oldest and simplest DBMS
model. The model is sorted hierarchically into a down or bottom-up design
approach. This model uses pointers to navigate between stored data.
Example of Hierarchical Model
5. Advantages
As the database is based on this
architecture the relationships
between various layers are
logically simple so, it has a very
simple hierarchical database
structure.
It has data sharing as all data
are held in a common database
data and therefore sharing of
data becomes practical.
It offers data security and this
model was the first database
model that offered data security.
Disadvantages
Even though this model is conceptually simple and
easy to design at the same time it is quite complex to
implement.
This model also lacks flexibility as the changes in the
new tables or segments often yield very complex
system management tasks. Here, a deletion of one
segment can lead to the involuntary deletion of all
segments under it.
It has no standards as the implementation of this
model does not provide any specific standard.
6. Network Model
This model is similar to the Hierarchical model, this model also uses pointers
toward data but there is no need for a parent-to-child association. It uses a
graph data structure. A child can have more than one parent. It has a one-to-
many or many-to-many relationship.
Example of Network Model
7. Advantages
In this model, we can
access the data easily,
and also there is a chance
that the application can
access the owner’s and
the member’s records
within a set.
This network does not
allow a member to exist
without an owner which
leads to the concept of
Data integrity.
Disadvantages
The design or structure of this model
is not user-friendly.
This model does not have any scope
for automated query optimization.
8. Relational Model
The relational model represents how data is stored in Relational
Databases. A relational database stores data in the form of relations
(tables). Consider a relation STUDENT with attributes ROLL_NO,
NAME, ADDRESS, PHONE, and AGE
Example of Relational Model
9. ADVANTAGES
As the database is based
on this architecture the
relationships between
various layers are
logically simple so, it has
a very simple
hierarchical database
structure.
It has data sharing as all
data are held in a
common database data
and therefore sharing of
data becomes practical.
It offers data security and
this model was the first
database model that
offered data security.
DISADVANTAGES
Even though this model is
conceptually simple and
easy to design at the same
time it is quite complex to
implement.
This model also lacks
flexibility as the changes in
the new tables or segments
often yield very complex
system management tasks.
It is also limited as many of
the common relationships
do not conform to the 1 to N
format as required by the
hierarchical model.
