2. Overview 1.DATA MODEL 2.RECORD-BASED DATA MODEL
2.1 THE HIERICHICAL MODEL
2.1.1 CHARACTERISTICS OF HIERICHICAL MODEL
2.1.2 DRAWBACK OF HIERARCHICAL MODEL
MADE BY: SEHRISH & HIRA
INSTRUCTOR: MAM NAZMEEN
COLLEGE : IMCG(P-G),G-10/4

3. Data models
A collection of raw facts and figures is called data. The word ‘raw’ means that the facts have not yet been processed to get their exact meaning .
A representation of real world objects ,events and their association is called a Model . The model helps the users to understand the complexities of real world environment .
A collection of concepts to describe and manipulate data ,relationship between data and constraints on data is called data model .

4. Record-based Data model
Record based models are basically used to describe the external and Conceptual levels of database .
The can also be used to describe the Internal level to some extent .
They are used to develop and specify the Logical Structure and provide some options for implementation of the design .
In record-based data model , database consists of different records .
Record may be of different types .
Each record type defines the Fixed number of fields .

5. Hierarchical Model Root Level-1 child Level-2
In this model ,records have a parent-child relationship.
One of the most popular hierarchical database management systems was information management system IMS.(introduced by IBM in 1968)
Root
Level-1
child
Level-2

6. Consider the application used for Production Planning in automobiles manufacturing companies .The model of database is shown in figure. The automobile manufacturer produces various car model. Each car model is decomposes in assemblies like Engines ,bodies and chassis .Each assembly Is further decomposed into sub-assemblies like valves ,spark , plugs and so on .
If the manufacturer wants To generate the Bill of materials for a particular model of automobile ,the hierarchical data model is Suitable because the bill of materials for a product has a hierarchical structure .
Each record represent a particular part. Since the records have a parent-child relationship, each part is linked to its sub-part.

7. Car
Body
Right door
Left door
Roof
Hood
Engine
Chassis

8. Characteristics of hierarchical model
Representation of data as hierarchical tree
Each sub-module has only one super-module
Represents a set of related records
Hierarchy through pointers
Simple structure
High performance
Predefined relationship between record types

9. Data as hierarchical tree
The hierarchical database is characterized by parent-child relationship between records.
A record type R1 is called parent of record type R2 if R1 is one level higher than R2 in the hierarchical tree .
The root of hierarchy is most important record type .
All record at different levels in hierarchy are dependent on the root .
Each child record has one parent record .
Parent record can have one or more child record. R1 R2 R3 R4 R5

10. Hierarchy through pointers
In hierarchical database , pointers are used to link the records .
Pointers determine whether the particular record occurrence is child or parent record.
The path from parent to child is maintained through pointers .
SIMPLE STRUCTURE
Database is simple hierarchical tree .
The parent and child records are stored close to each other on the disk.
It minimizes disk input and output.
HIGH PERFORMANCE & PREDEFINED RELATIONSHIP
The parent-child relationship is stored as pointer from one record to another .The navigation through the database is very fast resulting in high performance .
Records at different levels of the hierarchy are dependent on root record .

11. Drawbacks of hierarchical model
DIFFICULT TO REORGANIZE
It is difficult to reorganize the database because the hierarchy has to be maintained.
Each time a record is inserted or deleted ,the pointers have to be manipulated to maintain the parent-child relationship.
MORE COMPLEX REAL LIFE REQUIREMENTS
The hierarchical DBMS is based on a simple parent-child relationship. The real life applications are more complex and can not be represented by hierarchical structure .
E.G in an order-processing database , a single order might participate in three different parent-child relationship. It may link the order to customer who placed the order , the items ordered and sales person who took the order . This complex structure cannot be represented in hierarchical structure