By associating a specification with core Web-service elements, Design by Contract gives developers the ability at the design phase of development to reduce conceptual flaws and promote a better understanding of work scope, something that will be especially important in coming years as the Web-service environment becomes more and more dynamic.

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by Roger Smith, developer. Intel Corp.

By associating a specification with core Web-service elements, Design by Contract gives developers the ability at the design phase of development to reduce conceptual flaws and promote a better understanding of work scope, something that will be especially important in coming years as the Web-service environment becomes more and more dynamic.

Web services are a new breed of cat in software development. Self-contained, self-describing, modular applications that can be published, located, and invoked across the Internet, Web services are intended to automate a wide range of business functions, everything from providing stock quotes to processing credit card transactions to any of a 1,001 other services.

Above and beyond protocol squabbling, a software design principle that's been around for a while in various incarnations, Design by Contract, offers a unique perspective on what kind of design methodology to apply to Web services and how to best specify the components that make up Web services. (DbC was pioneered by Bertrand Meyer, creator of the Eiffel language; see Meyer's book, Object-Oriented Software Construction, Second Edition (Prentice Hall, 1997), for a more complete description of DbC.) By associating a specification with core Web-service elements, DbC gives developers the ability at the design phase of development to reduce conceptual flaws and promote a better understanding of work scope, something that will be especially important in coming years as the Web-service environment becomes more and more dynamic.

At their most generic, Web services are business processes that can be discovered and run over the Internet using agreed-upon standards such as XML and SOAP. As all but the most uninformed (and possibly unwashed) already know, SOAP currently stands for the Simple Object Access Protocol. I say "currently" because there is movement underfoot in the Microsoft camp to redefine the SOAP acronym as the "Service Oriented Architecture Protocol" as a way to give more respect to the underlying service-oriented architecture.