Extending Web Services Using Other Web Services

How to create a useful new Web service by tapping in to the power of two other freely available Web services.

Seasoned programmers rarely implement everything themselves. The days in which every application needed its own video and printer drivers, to say nothing of a filesystem or operating system, are long behind us. Instead, we now have hierarchies of software libraries, with each library making use of lower-level data and functions and also performing similar tasks for higher-level libraries.

Web services haven't changed the need for building new libraries on top of old ones. Indeed, we can expect to see an explosion of such new libraries in the future. The difference is that new libraries will often be based on Web services, which provide platform and language independence. We will see basic, middleware and high-level Web services, available from anywhere on the Internet and callable from any operating system or language. This month, we looked at one way in which we can create a new Web service out of an old one. Each call to our xmlrpc-lookup server fired off a query to Amazon's Web services. Information from Amazon was then combined with another data set, with results that are useful to anyone living in Skokie, Illinois. We can expect to see similar aggregating Web services in the future, both free of charge and for pay.

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Reuven M. Lerner, a longtime Web/database consultant, is currently a PhD student in Learning Sciences at Northwestern University in Evanston, Illinois. He and his wife recently celebrated the birth of their son Amotz David.