So, for example, suppose that an application, such as a global weather forecaster, needs to know the current outdoor temperature of Paris, France, as shown in the following figure.
Figure 20. Web services in action—a weather Web service
It might invoke a getTemp operation to obtain this information on a standard WorldWeather Web service located on the Internet in New York.
The WorldWeather Web service can provide this information to a client application, such as the global weather forecaster, as long as it is connected to the Internet and knows how to communicate as a Web service client. If this WorldWeather Web service acts, in turn, as a Web service client, it might also access standard LocalWeather Web services running in each city of the world. By invoking a getTemp operation on the appropriate LocalWeather Web service, the WorldWeather Web service can also return the current temperatures of New York, Moscow, or any other city to any Web service client application that requests it.
The LocalWeather Web service running in any one city can be built with a computer language and be running on a computer or operating system that is different from all others. As long as each LocalWeather Web service communicates with the Internet as a "standard" Web service, the WorldWeather Web service can get the information it needs to satisfy all client requests for city temperatures anywhere in the world that hosts LocalWeather Web services.
This scenario assumes that the WorldWeather Web service already knows the identity and location of all available LocalWeather Web services or has a way of locating any such Web service that it requires.
