Distributed Cooperative Caching In Social Wireless Networks,.

Distributed Cooperative Caching In Social Wireless Networks,.

Integrity constraints

Entity Integrity

The entity integrity constraint states that no primary key value can be null. This is because the primary key value is used to identify individual tuples in a relation. Having null value for the primary key implies that we cannot identify some tuples.This also specifies that there may not be any duplicate entries in primary key column key word

Referential Integrity

The referential integrity constraint is specified between two relations and is used to maintain the consistency among tuples in the two relations. Informally, the referential integrity constraint states that a tuple in one relation that refers to another relation must refer to an existing tuple in that relation. It is a rule that maintains consistency among the rows of the two relations.

Domain Integrity\

The domain integrity states that every element from a relation should respect the type and restrictions of its corresponding attribute. A type can have a variable length which needs to be respected. Restrictions could be the range of values that the element can have, the default value if none is provided, and if the element can be NULL.

User Defined Integrity

A business rule is a statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or influence the behavior of the business. E.g.: Age>=18 && Age<=60

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

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.