Chapter 1. Introduction to Web Services

The world is full of useful data and services offered by computer programs. But most of that data and most of those services are locked away. Web sites, designed for access by people and not programs, bury the information in an ever-changing morass of HTML. Communication protocols have been specific to applications and sometimes to operating systems. Precompiled libraries are useful only for particular programming languages on the system they were compiled for.

If you want to write a program to book a flight, check how much paid time off you have accrued, or find all the shows on TV that feature the stars of Buffy the Vampire Slayer , you're facing an uphill battle. All that data exists, but it's effectively inaccessible.

Sure, you could screenscrape HTML from web sites such as expedia.com and tvguide.com, but that puts you at the mercy of the web designers of those sites. Every time they decide to make their pages look prettier, you'll have to rewrite your screenscraper.

You might be able to wangle access to the machine that runs the payroll system, but it's unlikely . You might even know the programming language the payroll software was written in. But can you figure out the database structure?

Web services are all about enabling computers to communicate with each other, opening up services and data. Built on open standards, the way that the Web is, web services offer convenient standard ways to open up the functionality of your applications to other applications.

In this chapter you'll learn a bit about the history of web services and the current lie of the land ”what systems you can choose from, where the hype exceeds reality, and so on.