Various Types of Database Models

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1. Database Models

The initial development of data storage started with the file system and these files have actually no relation or information of the application using these files. These files are accessed through the application containing the information or name of the files so these files cannot be considered as database but used to store information about the database. The application software is not aware of the structure of the file but as compared to it database management system consists of metadata and it is the responsibility of metadata to translate the files in physical layer as well as creation of logical layer. Conceptually metadata is that data which is stored in the catalog of database that how data is stored in database and how relationship would be developed among data. The example of flat file system is just like an application dealing with customer records through cutomer_data.txt.
1.1 Hierarchical Database Management System

In hierarchical modeling technique the database is bit revolutionized and organized and the scheme is just like the record file indicating the address of certain data or pointing towards the place of actual record. The following example shows that two pointers are clearly pointing towards the web page and street address but for the pointer address or URL could be taken from the record which one step above the actual information or data.

Figure 7. Hierarchical Model
The relationship in this case is parent child with one parent and many children.
1.2 Network Database Management System

Network database model is somewhat similar to the hierarchical data model but this model is first time developed by CODASYL network although initial network database was Honeywell IDS but it was not stand...

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...ile developing this database as everything deals in logical way and any fact which is the part of real world but not presents in the database, never exists for the database.
Deductive database claims to adopt several properties of relational database and declarative property is one these properties. Declarative property is about querying or updating the information according to the requirement without knowing anything about operation. There are two important variations in the deductive database system and these are as follows
• Expert database system
• Knowledge based database system
In the pure deductive system data might be present in the both primary and secondary sections of the memory but in both of the above types data should be present in the primary section. Programming languages which is used to implement deductive system are known as Prolog and Data log.

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