Multi-tiered systems written today are usually highly customized for a particular business (a bank or a factory, for example), a particular brand of technology (such as Microsoft or Oracle), and a particular application (accounting or process control). Business invests in multi-million dollar software development projects with exacting requirements that often take years to complete. (If they finish at all. Some researchers claim that well over half of these mega-projects actually fail before being finished. Statistics on this are hard to get because businesses often cover up failures like these.)
For years, people have been trying to duplicate the success of the Internet and the web in other business applications to get away from the huge costs, inflexibility, and risks of business systems. One of the brightest hopes today is called web services. Web services actually consists of several interlocking technologies - some old and some new.
Using the already proven standards of XML and HTTP, different companies - with Microsoft in full cooperation - have been working to agree on a way for clients and servers to cooperate without a custom designed and programmed system. To date, they're doing pretty well. The Web Services Description Language (WSDL) is over five years old now and "everyone" seems to agree on it. Not long after, SOAP was standardized and is also in wide use. We used SOAP in a previous part of this series.
VB.NET 2008 and .NET 3.0 introduced a whole new organization to Web Services, however. The entire thing is now part of what Microsoft calls the Windows Communication Foundation (WCF). The templates that automate the use of Web Services aren't provided in the VB.NET 2008 Express system. (Although, as always, the .NET Framework that is the underlying source is still available.) In previous versions of VB.NET, you had to use separate Framework components such as ASP.NET Web Services (ASMX) along with the Web Service Enhancements (WSE) extensions, and the Microsoft Message Queue (MSMQ) to do the things that are now bundled into the single System.ServiceModel namespace.
A Real Production Web Service
To give you the idea behind web services, I recommend that you read about a real, production web service at the site at which it's offered. One of the best known web services is the Amazon Associates Web Service. (Go to Amazon.com, click on the Associates link at the bottom and select Web Service from the menu.) Using the Amazon Associates Web Service, you can make money for Amazon and yourself by programming your own web page to ...
- Retrieve detailed product information for all products being sold on Amazon.com.
- Create applications that use the same search featured in the "Advanced Search" option on Amazon
- Create customer reviews of products at Amazon
- Use community and merchandising tools at Amazon
- Retrieve product images
and
- use the Amazon "Shopping Cart" at your site.
Next - Collections of Things
The ability to program with collections of things is one of the key skills that must be mastered in programming. The real world is centered around the idea that things occur in collections. Think of how much harder it would be to shop if you couldn't buy "a dozen eggs" or a "bag of oranges". In part 10, Collections of Things, we show you how to do that in code!
