In-Depth

Book excerpt: A Web services guide

This book excerpt is from Chapter 2 of “Web Services: A Manager’s Guide” by Anne Thomas Manes, ISBN 0-321-18577-3, copyright 2003. All rights reserved. This chapter, titled “Web Services Basics,” is printed with permission from Addison-Wesley Professional.

If you ask five people to define web services, you’ll probably get at least six answers. Some people use the term “Web services” to describe applications that communicate with Simple Object Access Protocol (SOAP) (SOAP is an XML messaging protocol.) Other folks use the term to describe only the SOAP interface. Still other people vehemently object to the idea of constraining the definition to a specific technology such as SOAP. Some people use the term to describe any application that communicates over the Internet. Other people use the term to describe any Web-based application. Some people view Web services as anything that’s accessible over the Web. And some people use the term to describe the software-as-a-service business model.

Given that there is no official consensus within the industry, I am establishing my own set of names and definitions. I want to give you a basic grounding to help you understand this technology, so my goal is to make things as simple and straightforward as possible.

What is a Web service?

The simplest and most basic definition that I can give you is that a Web service is an application that provides a Web API. An API supports application-to-application communication. A Web API is an API that lets the applications communicate using XML and the Web.

So here’s the basic concept: Web services use the Web to perform application-to-application integration. A lot of the hype around Web services talks about dynamic assembly of Web-based software services. It talks about the software-as-a-service business model. It talks about spontaneous discovery of new business partners. My advice is to ignore this hype. It’s possible that at some point in the future some of these glossy images will become reality, but please don’t let the science fiction stories distract you from reality or dissuade you from using this technology today to solve real business issues.


Why Web services?

Rather than “what?,” I think the more important question is “why?” Why should you care about Web services? The answer is that Web services mitigate the application integration crisis. They help you integrate applications, and they do so at a significantly lower price point than any other integration technology.

Web services represent a new form of middleware based on XML and the Web. XML and the Web help solve the challenges associated with traditional application-to-application integration, which I call the Traditional Middleware Blues. To summarize:

* Traditional middleware doesn’t support heterogeneity.

* Traditional middleware doesn’t work across the Internet.

* Traditional middleware isn’t pervasive.

* Traditional middleware is hard to use.

* Traditional middleware is expensive.

* Traditional middleware maintenance costs are outrageous.

* Traditional middleware connections are hard to reuse.

* Traditional middleware connections are fragile.


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