Extending Web Services Using Other Web Services

摘要

Last month, we looked at the latest incarnation of Web services offered by on-line giant Amazon. Amazon was one of the first companies to embrace Web services, and although some of its newer offerings require payments on a monthly or per-query basis, basic catalog searches are still available free of charge. If we think of each individual Web service as a function call, we can think of a collection of Web services, such as Amazon Web Services (AWS), as a software library. And although we can certainly create interesting applications with such libraries, it is often useful to create new libraries that sit on top of the existing ones. In many ways, the history of software is the history of creating increasingly powerful abstractions by stacking libraries on top of one another. Outside of the classroom, most of us haven't ever had to implement a sort algorithm or create a buffered I/O library, simply because such things have been written and optimized by previous generations of programmers.