Mapping in Database
Mapping is a process of converting on level to another level. There are two levels of mapping: • From the conceptual level to the internal level • From the external level to the conceptual level [ad#ad-2] Conceptual / Internal Mapping: The conceptual/internal mapping defines the association between the abstract view and stored database. It specifies how conceptual records and fields are represented at the internal level. If stored data is changed with structural point of view, then the conceptual mapping must be changed accordingly so that the conceptual plan can remain steady. External / Conceptual Mapping: An external/conceptual mapping defines the correspondence between a ...
Three-Level Architecture
Database can he viewed at three levels. The levels form three-level architecture and are depicted by three models. The models refer to the permanent structure of the database, not to the data that is stored at any given moment. A database model is a collection of tools. It may include a type of diagram and specialized vocabulary for describing the structure of the database. The purpose of the three-level architecture is to separate the way the database is physically represented from the way the user thinks about it. [ad#ad-3] External Level: The external level consists of different external views of the database. ...
Relational Model
Dr. E. F. Codd worked to improve the working of DBMSs for handling large volumes of data. He applied the rules of mathematics for solving the problems of earlier database models. Some important problems were: • Data integrity • Data redundancy Dr. Codd presented a paper “A Relational Model of Data for Large Shared Databanks” in June I 970 that contained 12 rules. A DBMS that satisfies these rules is called a full Relational Database Management System (RDBMS). The term “Relation” is also derived from the “Set theory” of mathematics. [ad#ad-3] In a relational model, data is stored in relations. Relation is another term ...
The Network Model
To overcome the problems of the hierarchical data model, the Network Model was developed. The network model modified the hierarchical model by allowing multiple parent-child relationships. These relationships are known as sets in a network model. The network model structures and language constructs were defined by the CODASYL (Conference on Data Systems Language). [caption id="attachment_929" align="aligncenter" width="450" caption="The Network Model"][/caption] [ad#ad-3] 1. Characteristics of Network Model: The characteristics of a network DBMS are: 2. Data record types are represented as a network: In this model, data record types are represented as a network. 3. Each sub-module can have one or more super-modules: Since multiple ...
The Hierarchical Model
One of the earliest database management systems was based on the hierarchical model. In a hierarchical data model, the records have a parent-child relationship. Consider the application used for Production Planning in automobile manufacturing companies. The model of the database is shown in the following figure. The automobile manufacturer manufactures various models of cars. Each car model is decomposed into its assemblies (Engine, Body and Chassis). Each assembly is further decomposed into sub-assemblies (valves, spark plugs...), and so on. If the manufacturer wants to generate the Bill of Materials for a particular model of an automobile, the hierarchic data model would ...
Staged Database Design Approach
Another way to design an information system is known as staged database design approach. It is a top-down approach. It begins by analyzing the general requirements of the organization: As the process continues, these problems are analyzed in more details. The steps in this approach are as follows: [ad#ad-3] Analyze User Environment: The first step in designing a database is to understand and analyze the current user environment. The designer should closely study the current system and its outputs. He should also interview different users to know their current and future requirements. Develop Logical Data Model: After analyzing the user environment, the ...
System Development Life Cycle
System development life cycle (SDLC) is a conventional way for developing an. information system. It consists of many steps and involves different persons. Different step of SDLC are as follows: [caption id="attachment_912" align="aligncenter" width="488" caption="Phases of System Development Life Cycle"][/caption] Preliminary Investigation: Preliminary investigation is the first phase of System Development Life Cycle. The main objective of this phase is to identify deficiencies and requirements in the user’s current environment. An important result of the preliminary investigation is whether the system to be developed is feasible or not. Feasibility is determined on the following parameters: • Whether current technical resources or technology is ...
Database Development Process
The development of a complete database application is a lengthy and complicated process. Different strategies can be used to develop database applications. Following is a brief discussion about different strategies and steps performed during this process: [ad#ad-3] General Strategies: A database application is developed to satisfy the requirements of the user. It is very important to understand these requirements in detail. The application should be developed according to the expectation of the user. Different techniques are used to find the requirements and needs of the users such as interviews. These requirements should he defined as early as possible in the development ...
Types of Users in DBMS
There are different types of user that play different roles in a database environment. Following is a brief description of these users: (1) Application Programmers: Application programmer is the person who is responsible for implementing the required functionality of database for the end user. Application programmer works according to the specification provided by the system analyst. [ad#ad-3] (2) End Users: End users are those persons who interact with the application directly. They are responsible to insert, delete and update data in the database. They get information from the system as and when required. Different types of end users are as follows: Naive Users: ...
Range of Database Application
The range of database application is as follows: (1) Personal Computer Database: Personal computer databases are specially designed for single user. The user may be using stand-alone desktop computer or laptop. The representatives of a medical company may use laptop computers when working in the market. This computer may use a simple database application in which the records of customers are stored. Some important decisions about the development of personal computer database applications are as follows: • It should he purchased or developed within the organization? • It should be developed by end user or a professional in information system? • Required data ...
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