AJAX In Action [15]
This model of interaction has become quite deeply ingrained in our way of thinking over the ten years or so of the commercial, everyday Internet. Friendly WYSIWYG web-authoring tools visualize our site as a collection of pages. Serverside web frameworks model the transition between pages as state transition diagrams. The classic web application is firmly wedded to the unavoidable lack of responsiveness when the page refreshes, without an easy recourse to the asynchronous handler solution. Licensed to jonathan zheng Why Ajax rich clients? 15 But Amazon has built a successful business on top of its website. Surely the classic web application can’t be that unusable? To understand why the web page works for Amazon but not for everyone, we ought to consider usage patterns. 1.1.4 Sovereign and transient usage patterns It’s futile to argue whether a bicycle is better than a sports utility vehicle. Each has its own advantages and disadvantages—comfort, speed, fuel consumption, vague psychological notions about what your mode of transport “says” about you as a person. When we look at particular use patterns, such as getting through the rush hour of a compact city center, taking a large family on vacation, or seeking shelter from the rain, we may arrive at a clear winner. The same is true for computer UIs. Software usability expert Alan Cooper has written some useful words about usage patterns and defines two key usage modes: transient and sovereign. A tran- sient application might be used every day, but only in short bursts and usually as a secondary activity. A sovereign application, in contrast, must cope with the user’s full attention for several hours at a time. Many applications are inherently transient or sovereign. A writer’s word processor is a sovereign application, for example, around which a number of transient functions will revolve, such as the file manager (often embedded into the word processor as a file save or open dialog), a dictionary or spellchecker (again, often embedded), and an email or messenger program for communicating with colleagues. To a software developer, the text editor or Integrated Development Environment (IDE) is sovereign, as is the debugger. Sovereign applications are also often used more intensely. Remember, a wellbehaved UI should be invisible. A good yardstick for the intensity of work is the effect on the user’s workflow of the UI stalling, thus reminding the user that it exists. If I’m simply moving files from one folder to another and hit a two-second delay, I can cope quite happily. If I encounter the same two-second delay while composing a visual masterpiece in a paint program, or in the middle of a heavy debugging session with some tricky code, I might get a bit upset. Amazon is a transient application. So are eBay and Google—and most of the very large, public web-based applications out there. Since the dawn of the Internet, pundits have been predicting the demise of the traditional desktop office suite under the onslaught of web-based solutions. Ten years later, it hasn’t happened. Web page–based solutions are good enough for transient use but not for sovereign use. Licensed to jonathan zheng 16 CHAPTER 1 A new design for the Web 1.1.5 Unlearning the Web Fortunately, modern web browsers resemble the original ideal of a client for remote document servers about as closely as a Swiss army knife resembles a neolithic flint hunting tool. Interactive gizmos, scripting languages, and plug-ins have been bolted on willy-nilly over the years in a race to create the most compelling browsing experience. (Have a look at www.webhistory.org/www.lists/wwwtalk.1993q1/0182.html to get a perspective on how far we’ve come. In