-A travel agency has a web site. They serve online reservation and selling service for airline tickets. They work with three different airline companies which are X, Y and Z airways. A customer browse the main web page and he enters the desired destination and departure date to travel with airplane. This knowledge is sent to three airline companies, which respond if they serve for desired destination on this date and the price. After responding, the comparison is made to determine the airline company, which gives the cheapest price. After comparison OK message is sent to that company to reserve the ticket.