XML, Web Services, and the Data Revolution

By Frank  P.  Coyle

There is emergent behavior all around us. In chemistry the product of a chemical reaction is most often very different from any of its constituent ingredients . Consider sodium (Na) and chlorine (Cl), two volatile and dangerous chemicals that react violently when placed in proximity. Put sodium and chlorine together and, after the smoke clears, a totally new substance emerges: table salt (NaCl), not at all dangerous, in fact essential to human life.

That the Web arrived with the force of a chemical reaction is not an accident . Software designers and architects faced with the inability of over-designed systems to adapt to change have long sought alternatives to conventional systems building, which is based on the attempt to anticipate, up front, all possible system functionality and to building a system that satisfies a complete specification.

In an article entitled "Architectural Principles of the Internet," Brian Carpenter of the Internet Architecture Board's Network Working Group provides an informative description of the architectural philosophy underlying the Web:

In searching for Internet architectural principles we must remember that technical change is continuous. In this environment, some architectural principles in evitably change. Principles that seemed inviolable a few years ago are deprecated today. Principles that seem sacred today will be deprecated tomorrow. The principle of constant change is perhaps the only principle of the Internet that should survive indefinitely. ^[1]

^[1] Brian Carpenter, "Architectural Principles of the Internet," Request for Comments 1958, Internet Architecture Board, June 1996, http://www.isi.edu/in-notes/rfc1958.txt.

On simplicity and modularity, he has this to say: "Keep it simple. When in doubt during design, choose the simplest solution." He adds, "Modularity is good. If you can keep things separate, do so."

As you work your way through the various chapters of this book, it's important to keep in mind that simplicity, modularity, and emergent behavior are the driving forces behind the technology revolution that surrounds the Web, XML, and Web services.

For the big players in the software industry, the difficulty is predicting the effects of a software chemical reaction. Consider for a moment the Napster phenomenon . Napster, the Web-based, peer-to-peer music distribution system, exploded on the scene almost overnight, not planned or designed in the traditional software sense, but emerging from the assembly of a loosely coupled network infrastructure plus some simple parts . Despite legal attacks on the Napster, the genie is out of the bottle . The music industry will never be the same. Nor will the software industry.

The major industry players, now well aware of the power of emergent software, are driven both by both desire and fear: the desire to leverage the Web to enhance their bottom lines, but also the fear that if they aren't experimenting with new combinations and possibilities, new technologies will emerge from the primordial software soup and make what they are doing obsolete.