Web services are based on a service oriented architecture. Service-oriented architecture allows a service provider to easily integrate with the consumer of that service. Web services enable different applications to share data and functionality amongst themselves. It allows consumers over the internet to access data without the application knowing the format or the location of the data.
This becomes extremely critical when you don't want to expose the data model or the logic used to access the data but still want the data readily available for its consumers. An example would be a web service exposed by a stock exchange. Online brokers can use this web service to get real time information about the stocks and display them on their own websites for end users to buy. The broker website only needs to call the service and request the data for a company. When the service replies back with the data, the web application can parse the information and display it.
Web services are platform...
