Recently someone asked in the comments to one of my posts why I seem to be down on the WS-* family of technologies (XSD, WSDL, SOAP, etc) when just a few years ago I worked on Microsoft’s implementations of some of these technologies and used to blog about them extensively.

I was composing a response when I stumbled on James Snell’s notes on the recent QCon conference that captures the spirit of my “conversion” if you want to call it that. He wrote

Those who are familiar with my history with IBM should know that I was once a *major* proponent of the WS-* approach. I was one of the original members of the IBM Emerging Technologies Toolkit team, I wrote so many articles on the subject during my first year with IBM that I was able to pay a down payment on my house without touching a dime of savings or regular paycheck, and I was involved in most of the internal efforts to design and prototype nearly all of the WS-* specifications. However, over the last two years I haven’t written a single line of code that has anything to do with WS-*. The reason for this change is simple: when I was working on WS-*, I never once worked on an application that solved a real business need . Everything I wrote back then were demos. Now that I’m working for IBM’s WebAhead group, building and supporting applications that are being used by tens of thousands of my fellow IBMers, I haven’t come across a single use case where WS-* would be a suitable fit. In contrast, during that same period of time, I’ve implemented no fewer than 10 Atom Publishing Protocol implementations , have helped a number of IBM products implement Atom and Atompub support, published thousands of Atom feeds within the firewall, etc. In every application we’re working on, there is an obvious need to apply the fundamental principles of the REST architectural style. The applications I build today are fundamentally based on HTTP, XML, Atom, JSON and XHTML.

My movement towards embracing building RESTful Web services from being a WS-* advocate is based on my experiences as someone who worked on the fundamental building blocks of these technologies and then as someone who became a user of these technologies when I moved to MSN Windows Live. The seeds were probably sown when I found myself writing code to convert Microsoft’s GetTopDownloads Web service to an RSS feed because the SOAP Web service was more complicated to deal with and less useful than an RSS feed. Later on I realized that RSS was the quintessential RESTful Web service and just asking people “How many RSS feeds does Microsoft produce?” versus how many SOAP endpoints does Microsoft expose is illuminating in itself.

Since then we’ve reached a world where thousands of applications being utilized by millions of end users are built on RESTful Web services on the public internet. My favorite example of the moment is the Facebook developer platform and before that it was Flickr and Amazon S3. Compare that with the number of SOAP and WS-* interfaces that are being used to build real developer platforms that benefit end users on the Web today.

Earlier today, I was contemplating Don Box’s recent post where he complained about the diversity of authentication schemes of various RESTful Web services from the “J. Random Facebook/Flickr/GData” services on the Web today. Don seems to hint that WS-Security/WS-Trust would somehow solve this problem which is rightfully debunked by Sam Ruby who points out that all those technologies do is give you a more complicated version of the extensible authentication story that is available in HTTP. So the only real issue here is that there are actually enough RESTful Web services on the Internet for Don Box to complain about the diversity that comes from having a flexible authentication model for Web services. On the other hand, there are so few useful public WS-* Web services on the Web (read: zero) that Don Box hadn’t encountered the same problem with WS-Security/WS-Trust since no one is actually using them.

At this point I realize I’m flogging a dead horse. The folks I know from across the industry who have to build large scale Web services on the Web today at Google, Yahoo!, Facebook, Windows Live, Amazon, etc are using RESTful Web services. The only times I encounter someone with good things to say about WS-* is if it is their job to pimp these technologies or they have already “invested” in WS-* and want to defend that investment.

At the end of the day, my job is to enable successful developer platforms that enrich our users’ lives not pimp a particular technology. So if you are one of my readers and were wondering what was behind my shift from thinking that WS-* related technologies were the cat’s pajamas and my current RESTful Web services/APP/GData/Web3S bent, now you know.

Enjoy.

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