Data Models
A data model is a
collection of concepts that can be used to describe the structure of a
database. Or, we can say, Data model is a way of storing and retrieving the
data. There are different data models. Data models differ in the way they allow
users to view and manipulate relationships between entities. Each has its own
way of storing the data. The following are the different data models:
The hierarchical model
The
data is sorted hierarchically, using a downward tree. This model uses pointers
to navigate between stored data. It was the first DBMS model.
In
other words, In this model, data is stored in the form of a tree. The data is represented by parent-child
relationship. Each tree contains a single root record and one or more subordinate
records.
This
model supports only one-to-many relationship between entities.
The network model
Like
the hierarchical model, this model uses pointers toward stored data. However,
it does not necessarily use a downward tree structure.
Data
is stored along with pointers, which specify the relationship between entities.
This model is complex. It is difficult to understand both the way data is
stored and the way data is manipulated.
It is capable of supporting many-to-many relationship between entities,
which hierarchical model doesn’t.
The relational model
(RDBMS)
This
stores data in the form of two-dimensional table. Table is a collection of rows
and columns. The data is manipulated based on the relational theory of
mathematics.
The deductive model
Data
is represented as a table, but is manipulated using predicate calculus.
The object model (ODBMS,
object-oriented database management system)
The
data is stored in the form of objects, which are structures called classes that
display the data within. The fields are instances of these classes.
No comments:
Post a Comment