From an Excel perspective, web services are primarily useful for retrieving variable data over the Internet, but you can also use them to send data, to manipulate remote data, or to run other code on remote computers. Web services are designed to work just like procedure calls from code, so it is possible to use a web service without even knowing that it is running remote code.
That’s possible, but it’s not likely, since web service methods often rely heavily on their underlying foundation: XML. That means Excel programmers must become familiar with the Microsoft XML type library before they can effectively use web services. The good news is that, once you are comfortable working with XML, you can blast web service results directly into spreadsheet lists using Excel XML maps (which is very cool).
Web services, like many Internet-related things, are part of evolving standards. These standards have broad support by many companies, so web services are not likely to lose support in the future. However, since the standards are still evolving, there are different approaches to implementing, locating, and accessing web services. Of specific interest to Excel developers are the facts that: