Introduction to database management systems

A model is an abstraction process which hide superfluous details. Data modeling is

Used for representing entities and their relationship in database. Data  model  is  a  collection  of  concepts  which is used  to  describe  structure  of  a database which provides necessary means to abstraction. The structure of a database means that holds the data.

Types of Data Models 

• High Level- Conceptual Data Model
• Low Level – Physical Data Model
• Relational or Representational
• Object-Oriented Data Model
• Object-Relational Model

High  Level-conceptual  Data  Model:  User  level  data  model  is  high  level  or conceptual  model.  It  provides  concepts  which  are  close  to  way  that  many users perceive data. 

Low level-Physical Data Model: It provides concepts that describe details of how data is stored in computer model.  Low-level data model is only for Computer specialists not for end-user. 

Representation Data Model: It is between High level & Low level data model which provides concepts that may be understood by end-user but that are not too far removed from way data is organized by within computer.  The most common model are: 

• Relational Data Model : The Relational Model  uses  a  collection  of  tables  and  relationship among  those tables. Tables have  multiple  columns and  each  column  has  a  unique name. The  main  advantage  of  this  model  is its ability to represent  data  in  a  simplified format. The  process  of  manipulating  record  is  simplified  with  use  of  certain  key attributes used to retrieve data. 
  
  
  
  image source: wikimedia

• Network Model: The data   in   network   model   are   represented   by collection   of   records and relationships among data are represented by links, which can be viewed as pointers. The records in the database are organized as collection of arbitrary groups. The main advantage of this model is its representation of relationships between entities is implemented using pointers which allows representation of arbitrary relationship. 
  
  
  image source: wikimedia

• Hierarchy Model: A hierarchical data model the data is organized into a tree-like structure. The structure allows repeating information using parent/child relationships: each parent can have many children, but each child only has one parent.
  
  
  
  
  

• Object-Oriented Data Model: A data model is a logic organization of the real world objects (entities), constraints on them, and relationships among objects. A DB language is a concrete syntax for a data model. Example OBJECTSTORE or VERSANT

• Object-Relational Model: 

  The object-oriented database product largely consists of classes, objects and inheritance that are supported in database schemas and in query language.