DBMS

a. Data:

·         It is a collection of information.

·         The facts that can be recorded and which have implicit meaning known as 'data'.

·         Example:

                 Customer  ----- 1.cname.

                                               2.cno.

                                               3.ccity.

b. Database:

·         It is a collection of interrelated data.

·         These can be stored in the form of tables.

·         A database can be of any size and varying complexity.

·         A database may be generated and manipulated manually or it may be computerized.

·         Example:

 Customer database consists the fields as cname, cno, and ccity

Cname	Cno	Ccity

c. Database System:

1.What are the advantages of a database system over conventional file processing systems? (8 Marks, April-2000)

·         It is computerized system, whose overall purpose is to maintain the information and to make that the information is available on demand.

·         Advantages:

                  1.Redundency can be reduced.

                  2.Inconsistency can be avoided.

                  3.Data can be shared.

                  4.Standards can be enforced.

                  5.Security restrictions can be applied.

                  6.Integrity can be maintained.

                  7.Data gathering can be possible.

                  8.Requirements can be balanced.

d. Database Management System (DBMS):

1.What are the advantages of DBMS over File processing systems?

                       

File Processing System:

·         It is a collection of interrelated data and programs to access the data.

·         It is a collection of programs that enables users to create and maintain a database.

·         It is a 'General Purpose Software System’ that facilitates the processes of Defining, Constructing and Manipulating databases for various applications.

·         Advantages:

1.Data Independence.

2.Efficient Data Access.

3.Data Integrity and security.

4.Data administration.

5.Concurrent access and Crash recovery.

6.Reduced Application Development Time.

·         Dis-advantages:

1.Data Redundancy.

2.Data Inconsistency.

3.Difficulty in accessing the data.

4.Data Isolation.

5.Security Problems.

LEVELS OF DATA ABSTRACTION 

 This is also called as 'The Three-Schema Architecture’, which can be used to separate the user applications and the physical database.

1.Physical Level:

·         This is a lowest level, which describes how the data is actually stores.

·         Example:

                        Customer account database can be described.

2.Logical Level:

·         This is next higher level that describes what data and what relationships in the database.

·         Example:     

               Each record

                       type customer = record

                                   cust_name: sting;

                                         cust_city: string;

                                         cust_street: string;

                              end;

3.Conceptual (view) Level:

·         This is a lowest level, which describes entire database.

·         Example:

                        All application programs.

                       

DATA MODELS

·         The entire structure of a database can be described using a data model.

·         A data model is a collection of conceptual tools for describing

·         Data models can be classified into following types.

1.Object Based Logical Models.

2.Record Based Logical Models.

3.Physical Models.

Explanation is as below.

1.Object Based Logical Models:

·         These models can be used in describing the data at the logical and view levels.

·         These models are having flexible structuring capabilities classified into following types.

a.       The entity-relationship model.

b.      The object-oriented model.

c.       The semantic data model.

d.      The functional data model.

2.Record Based Logical Models:

·                     These models can also be used in describing the data at the logical and view levels.

·                     These models can be used for both to specify the overall logical structure of the database and a higher-level description.

·                     These models can be classified into,

1.   Relational model.

2.   Network model.

3.      Hierarchal model.

3. Physical Models:

·         These models can be used in describing the data at the lowest level, i.e. physical level.

·         These models can be classified into

a.       Unifying model

b.      Frame memory model

.

5.Entity Relational Model (E-R Model)

                     The E-R model can be used to describe the data involved in a real world enterprise in terms of objects and their relationships.

Uses:

·                     These models can be used in database design.

·                     It provides useful concepts that allow us to move from an informal  

               description to precise description.

·                     This model was developed to facilitate database design by allowing the specification of overall logical structure of a database.

·                     It is extremely useful in mapping the meanings and interactions of real world enterprises onto a conceptual schema.

·                     These models can be used for the conceptual design of database

                  applications.

B2C and B2B Community Overview

B2C

 Large in number
 Users share an
experience
 Focus on low-touch
services
 Grows by mass adoption
 Forums, ratings and selfserve
offering
 Typically quick to scale
but users have weak ties
 Vague mission: it is
interpretive

B2B

 Number can vary
 Members share a purpose
 Focus on high-touch
services
 Grows by word of mouth
trust
 Programmatic
membership offering
 Typically slow to scale but
members have stronger
ties
 Strong stated mission
that is visibly embraced

E-Commerce Models

E-Commerce Models

•Business to consumer (B2C)

–Targets consumers or end users, and sells products and/or services

•Amazon.com, small business sites

•Business to business (B2B)

–Helps organizations to manage relationships and transactions with other businesses

•B2BExchange

•Consumer to consumer

–Not a traditional B2C model

•eBay

E-commerce security

E-commerce security

E-commerce Security is a part of the Information Security framework and is specifically applied to the components that affect e-commerce that include Computer Security, Data security and other wider realms of the Information Security framework.

Traditional Commerce

Traditional Commerce  vs. E-Commerce

•Similarities

–Both aim to deliver a valued product or service

–Both want to serve a large audience

–Both strive to quickly deliver products and services

•Differences

–E-commerce customers expect shorter fulfillment time

–E-commerce customers must understand Web-based technologies

–E-commerce provides a global audience

–E-commerce orders are processed without human interaction or travel to a store location

–E-commerce relies upon encryption for security

RDBMS=== LECTURE CLASS I

===========================================

1. What is DBMS? Explain its features.

====================================

A. In a typical file processing system, permanent records are stored in various files. A

number of different application programs are written to extract records from and add recordsto the appropriate files. But this method has a number of disadvantages, such as DataRedundancy, Difficulty in access, Data Isolation, Concurrent Access, Security Problems, andIntegrity Problems..

A Database Management System (DBMS) consists of a collection of interrelated data and a set of programs to access this data. This collection of Data is called Database. The Primary goal of a DBMS is to provide a convenient environment to retrieve and store database information.

Features of DBMS:-

=========================================

1.

The integration and sharing of data files minimizes the duplication and redundancy of

data to a great extent.

2.

Integration of data files also results in a considerable saving of storage space and in

data entry and data storage costs.

3.

Fewer application programs need to be developed for obtaining various reports due to independence of programs and data.

4.

The query language facility helps non-programming persons to access the database

for information as needed without the help of any programmer.

5.

Faster preparation of information to support non-recurring tasks and changing

conditions is possible.

6.

Updation of data becomes easier due to integration of data file. Fewer errors may

when several records may be updated simultaneously.

7.

Large database maintenance.

Software Engineering

Software Engineering is concerned with

•  Technical processes of software development
•  Software project management
•  Development of tools, methods and theories to support software production
•  Getting results of the required quality within the schedule and budget
•  Often involves making compromises
•  Often adopt a systematic and organized approach
•  Less formal development is particularly appropriate for the development of web-based systems

Software Engineering is important because

•  Individuals and society rely on advanced software systems
•  Produce reliable and trustworthy systems economically and quickly
•  Cheaper in the long run to use software engineering methods and techniques for softwaresystems

Fundamental activities being common to all software processes:

•  Software specification: customers and engineers define software that is to be produced and the constraints on its operation
•  Software development: software is designed and programmed
•  Software validation: software is checked to ensure that it is what the customer requires
•  Software evolution: software is modified to reflect changing customer and market requirements

Software Engineering is related to computer science and systems engineering:

 Computer science

o Concerned with theories and methods

 Software Engineering

o Practical problems of producing software

 Systems engineering

o Aspects of development and evolution of complex systems

o Specifying the system, defining its overall architecture, integrating the different parts to 

create the finished system

General issues that affect many different types of software:

 Heterogeneity

o Operate as distributed systems across networks

o Running on general-purpose computers and mobile phones

o Integrate new software with older legacy systems written in different programming 

languages

o Challenge: build dependable software that is flexible enough to cope with heterogeneity

 Business and social change

o Change existing software and rapidly develop new software

o Traditional software engineering techniques are time consuming

o Goal: reduce time to adapt to changing needs

 Security and trust

o Software is intertwined with all aspects of our lives

o See remote software systems (web page, web service interface)

o Make sure malicious users cannot attack software and information security is 

maintained

Essential attributes of good software

 Maintainability

 Dependability and security

 Efficiency

 Acceptability

Application types

 Stand-alone applications

 Interactive transaction-based applications

 Embedded control systems

 Batch processing systems

 Entertainment systems

 Systems for modeling and simulation

 Data collection systems

Types of Programming Language

Low Level Language

• First-generation language is the lowest level computer language. Information is conveyed to the computer by the programmeras binary instructions
• Binary instructions are the equivalent of the on/off signals used by computers to carry out operations. The language consists of zeros and ones.

Advantages

Ø  Fast and efficient

Ø  Machine oriented

Ø  No translation required

     Disadvantages

Ø  Not portable

Ø  Not programmer friendly

Assembly Language

Assembly or assembler language was the second generation of computer language. By the late 1950s, this language had become popular. Assembly language consists of letters of the alphabet. This makes programming much easier than trying to program a series of zeros and ones. As an added programming assist, assembly language makes use of mnemonics, or memory aids, which are easier for the human programmer to recall than are numerical codes.

Assembler

An assembler is a program that takes basic computer instructions and converts them into a pattern of bits that the computer's processor can use to perform its basic operations. Some people call these instructions assembler language and others use the term assembly language In other words An assembler is a computer program for translating assembly language — essentially, a mnemonic representation of machine language — into object code. A cross assembler (see cross compiler) produces code for one processor, but runs on another.

As well as translating assembly instruction mnemonics into opcodes, assemblers provide the ability to use symbolic names for memory locations (saving tedious calculations and manually updating addresses when a program is slightly modified), and macro facilities for performing textual substitution — typically used to encode common short sequences of instructions to run inline instead of in a subroutine.

High Level Language

The introduction of the compiler in 1952 spurred the development of third-generation computer languages. These languages enable a programmer to create program files using commands that are similar to spoken English. Third-level computer languages have become the major means of communication between the digital computer and its user. By 1957, the International Business Machine Corporation (IBM) had created a language called FORTRAN (FORmula TRANslater). This language was designed for scientific work involving complicated mathematical formulas. It became the first high-level programming language (or "source code") to be used by many computer users.

Within the next few years, refinements gave rise to ALGOL (ALGOrithmic Language) and COBOL (COmmon Business Oriented Language). COBOL is noteworthy because it improved the record keeping and data management ability of businesses, which stimulated business expansion.

Advantages

Ø  Portable or machine independent

Ø  Programmer-friendly

Disadvantages

Ø  Not as efficient as low-level languages

Ø  Need to be translated

Examples : C, C++, Java, FORTRAN, Visual Basic, and Delphi.