During last August's Agile 2010 conference, I attended a session that used a board game to simulate the collaboration between developers and UX professionals. The object of the game was to coordinate the schedules of these two groups, who normally follow the beats of different metronomes. On top of that basic timing challenge, unexpected events complicated this dance between development and UX.

While this session does show a novel application of serious gaming (one of my favorite topics, in case you hadn't noticed), the interesting aspect of this session is that it happened at all. Until recently, UX was not a major concern for Agilists – or most people developing software, for that matter. The phrase, "And then we'll throw a UI on top of it," summarized the indifference of all too many development teams to UX concerns.

In the last few years, many teams have learned a new attitude. Instead of treating UX as a tarpaulin, thrown over the application to clumsily hold it all together, UX is as much a part of the system as the technical architecture or the application logic.

In fact, the newly-discovered appreciation for UX has proceeded far enough that it's time to start treating UX as its own application layer. That's what Erik Larson of Adobe argued at a discussion between Adobe and industry analysts about a month ago. Larson's basic point was that UX is an intrinsic part of the application, not an extrinsic afterthought. It not only defines the face of the application that the user sees, but it also may include the sensors that detect and record how that person uses the application. (That actually sounds like two layers, not one, but there's no need to split hairs just yet.)

Traditionally, measuring usage was something that IT departments did – and not as frequently as they should– to gauge the return on their technology investment. Now, with the advent of SaaS, actual usage is a powerful business imperative for both customers and vendors. Customers still want to measure the return on their investment, measured in number of active licenses and other obvious statistics. Vendors, too, want to calculate the value of their investments, measured by the number of users who have accessed new features or the percentage of trial users who become paying customers.

The technology industry is perhaps 30 years late in realizing the importance of real adoption, not transitory sales, for their business, but here we are. The poor adoption rates of many technology sectors (for example, the half of content management projects that fail, a statistic that didn't budge in spite of a decade of product development) are no longer tolerable. The economic problem for customers is obvious: What if you bought a car, and only had a 50/50 chance of actually driving it off the lot? For vendors, the economic problems of low usage can be just as dire.

For example, as our research shows, if you want to be a thought leader, you'd better have a healthy portfolio of success stories. For many tech vendors, pulling together that portfolio for significant events, such as a product launch, often required a mad scramble to find someone, anyone, to say nice things about the newest version of a product. When wackiness ensues like this, the business results are rarely close to satisfactory.

The business value of real adoption is only one reason that technology companies have this newfound appreciation for UX. However many one might cite (and I can think of several), UX has ascended from the sub-basement of development priorities. Some signs of it are subtle, such as the quiet fashion in which user stories, as part of Agile methodologies, re-defined how development teams conceived their own projects. Others are fairly obvious, such as when a vendor like Intuit refuses to take on a new project unless it passes a UX-heavy justification gauntlet that starts with a narrative about a specific customer and use case, and ends with a potential user giving feedback on a mockup or storyboard.

Treating UX as an application layer, as Adobe's Erik Larson proposed, is more profound than just adding an eighth layer to the OSI model. It's a sign of a profound change in the technology industry, in which the connection between user and developer, consumer and producer, business and technology is far stronger today than in more primitive times, when it was acceptable for a development manager to say, "And then we'll throw a UI on top of it."