Skip to main content

Database Architecture

Data Abstraction


The major purpose of a database system is to provide users with an abstract view of the system. The system hides certain details of how data is stored, created and maintained. Complexity should be hidden from the database users, which is known as Data Abstraction. 

Levels of Abstraction :

A common concept in computer science is levels (or less commonly layers) of abstraction, where in each level represents a different model of the same information and processes, but uses a system of expression involving a unique set of objects and compositions that are applicable only to a particular domain. Each relatively abstract, a "higher" level builds on a relatively concrete, "lower" level, which tends to provide an increasingly "granular" representation. For example, gates build on electronic circuits, binary on gates, machine language on binary, programming language on machine language, applications and operating systems on programming languages. Each level is embeded, but not determined, by the level beneath it, making it a language of description that is somewhat self-contained.

Database Users in Database Management System


The Database Users fall into several categories : Application Programmers are computer professionals interacting with the system through DML calls embedded in a program written in a host language (e.g. C, PL/1, Pascal) :
 
These programs are called Application Programs.

The DML Precompiler converts DML calls (prefaced by a special character like $, #, etc.) to normal procedure calls in a host language.

The host language compiler then generates the object code.
Some special types of programming languages combine Pascal-like control structures with control structures for the manipulation of a database.

These are sometimes called Fourth-Generation Languages.

They often include features which to generate forms and display data. Sophisticated Users interact with the system without writing programs

 They form requests by writing queries in a database query language.

 These are submitted to a query processor that breaks a DML statement down into instructions for the database manager module. 

Specialized Users are sophisticated users writing special database application programs. These may be CADD systems, knowledge-based and expert systems, complex data systems (audio/video), etc

. Naive Users are unsophisticated users who interact with the system by using permanent application programs (e.g. automated teller machine).

Labels

Labels:

Popular posts from this blog

What is iostream.h in C++ Programing Language ?

In C++ programing language, all header files end with .H extension. In standard C++, all devices are accessed and used as a file.  One such header file is iostream.h in C++ programming language. In this, all input and output devices are treated as files.  Let's quickly look at what are the input and output devices mean in C++ program.  Standard Input Device - Keyboard  Standard Output Device   - Monitor  Standard Error Device - Screen or monitor In C++, input and output are not defined within, and are implemented with the help of a component of the C++ standard library which is I/O library.  A file is read simply as a stream of bytes at the lowest level. But at a user level, a file consists of possibly mixed data types which can be characters, arithmetic values class, objects etc.  What are the predefined streams in I/O Library? As discussed above there are input, output and error library in c++, they have some predefined streams objects as well w...
Read more

C++ Program to find the sum, difference, product and quotient of two integers

#include <iostream.h> #include <conio.h> void main() {   clrscr();   int x = 10;   int y = 2;   int sum, difference, product, quotient;   sum = x + y;   difference = x - y;   product = x * y;   quotient = x / y;   cout << "The sum of " << x << " & " << y << " is " << sum << "." << endl;   cout << "The difference of " << x << " & " << "y <<  is " << difference << "." << endl;   cout << "The product of " << x << " & " << y << " is " << product << "." << endl;   cout << "The quotient of " << x << " & " << y << " is " << quotient << "." << endl;   getch(); }
Read more

What is Dynamic Memory Allocation in C++ Program

In the computer world, anything that is processed be it an instruction or any data first needs to be loaded and located in internal memory.  In C++ programs also any data that is processed while executing the program is held in the internal memory.  What is Dynamic Memory Allocation? Dynamic Memory allocation means that the memory that will be used during the program is not known beforehand and is allocated dynamically and on the go. It is allocated during the runtime as and when required by the program. In C++ there are two operators used in dynamic memory allocation  1. New  2. Delete New operator in dynamic memory allocation The new operator in C++ is used to create objects of all types. The new operator will allocate memory of the size of the data type specified in the program.  For Example iptr = new int ;  Storing initial values will allocate needed amount of memory from the free store to hold the value of the specified data-type and store the startin...
Read more