Ajax in Action. Chapter 6: The User Experience
Ajax in Action. Chapter 6: The User Experience
Written by Dave Crane and Eric Pascarello with Darren James and reproduced from "Ajax in Action" by permission of Manning Publications Co. ISBN 1932394613, Copyright 2005. All rights reserved. See http://www.manning.com for more information.
This chapter covers
In chapter 1, we discussed usability, the keystone to any software application. No matter how well organized your codebase and how clever the technical merits of your application, if the usability stinks, you leave a bad association in the user's mind. This can be grossly unfair, but it's a fact of life. More people recognize Albert Einstein for his hangdog looks and wild hair than understand what he was trying to say about the nature of space-time. First impressionsand attention to detailmatters.
In chapters 2 to 5, we introduced a lot of cool technology and did some clever things with Ajax. The focus on organization throughout the latter part of this journey has enabled us to be flexible and highly adaptive about how we do these things. However, our examples have been rather rough around the edges, and rightly so while we focused on the cleverness at hand, but now we need to step back and assess what we have done in terms of creating something that people will actually want to use, possibly for several hours a day. The topics presented in this chapter will go a long way toward helping you get your Ajax application ready and presentable for the real world.
One of the biggest things that you can do to make your users feel comfortable with your application is to keep them informed about background events in a discrete and consistent fashion. They aren't the be-all and end-all of usability, but we will focus on them in this chapter in order to show how an in-depth, consistent treatment benefits the application as a whole. Most Ajax applications will want to notify the user at some point too, so we hope you'll find the finished components useful in your own projects as well.
We develop several solutions in this chapter for letting the users know what is going on, without getting in the way of their workflow. Before we go into these specifics, though, let's take a quick look at what we mean by quality and how to get there.
6.1 Getting it right: building a quality application
Usability is an especially hot topic for Ajax because web app users can be an extremely fickle bunch. The downside of being able to download and run your app with zero effort is that the users have invested no time and effort in it when they start to use the application and will be willing to throw it away and move on to the next of the 8 billion web pages that Google can point them to. To complicate matters further, with Ajax we are seeing the convergence of two different usability traditions, namely the desktop application and the web page. Getting the mixture right can be quite a challenge, and failing to get it right can consign your hard work to obscurity.
In chapter 1, we looked at usability from the users' point of view. What do they want in an application? And what are they willing to put up with? Let's turn the question around now and ask what qualities we need in our code to meet the goal of usability. With this as a starting point, we can figure out what we can do in practical terms to make our application work. The following sections detail a number of key features that add quality to your application.
The most basic frustration that a computer user can suffer from is to have workflow interrupted while the computer struggles to catch up with him. Basic design mistakes, such as locking up the entire user interface while writing some lengthy configuration file to disk, can cause the user to lose track of what he is doing and force him to make the mental leap between the domain model in which he is engaged to the harsh reality of computer hardware.
When looking at responsiveness, it can be important to understand your target audience and its typical system setups. In the case of writing a configuration file, the speed may be acceptable on the developer's high-speed 7200-RPM SATA disk drive on the local workstation, but the customer writing the file to a congested network share or a USB thumb drive may have a different experience. In the specific case of web app development, a similar mistake is often made in only testing the application running over the loopback interface, that is, the web server running on the same development machine as the web browser. This doesn't give a useful evaluation of network latency issues, and all web apps ought to be either tested over a real LAN or WAN or simulated using a traffic-shaping tool.
Beyond network issues, the performance of the client code can make a huge difference to responsiveness. Performance is a big issue, so we'll defer a closer look at it to chapter 7.
An application is robust if it can withstand the usual conditions encountered at a busy workstation. How does it cope with a temporary network outage? If a badly behaved program hogs the CPU for five minutes, will your application still work afterwards? At one recent project that I was involved in, we would test our application's robustness by pounding randomly on the keyboard for 10 seconds or so, and by "scribbling" the mouse across the page while clicking it. A crude sort of testbut effectiveand quite good fun!
What can such a test reveal? For one thing, it can highlight inefficiencies in event-handler code. Keypresses, mouse moves, and the like need to return quickly, since they are apt to be called very frequently. Further, they can reveal unintentional dependencies between components. A particular condition may arise in a GUI, for example, where a modal dialog is blocking access to the main application, but an open menu item is blocking access to the modal dialog. If such a situation depends on precise timing in the opening of the dialog and the menu, it might take a single user two months of daily work to discover it. Once released to an audience of several thousand, however, it might start showing up within hours and be extremely hard to reproduce from field reports. Identifying the problem up front, and correcting it, increases the overall robustness of the application.
There is more to robustness than randomly thumping the keyboard. Just as valuable is the process of watching someone other than the developer trying to use the application. In the case of a complete newcomer, this can provide helpful information on the overall usability design, but it is also useful to let someone closely acquainted with the domain knowledge, even the product, test-drive a new bit of functionality. When the person who wrote the code runs the program, she can "see" the code behind it and may subconsciously avoid specific combinations of actions or particular actions in specific contexts. The end user won't have this insider knowledge, of course, and neither will the developer sitting next to you (unless you do pair programming). Getting someone else to informally run through your app workflow can help to build up robustness early on.
As we already noted, the usability patterns of Ajax are still evolving from a mishmash of desktop application and web browser conventions. Some Ajax toolkits, such as Bindows, qooxdoo, and Backbase, even present widget sets deliberately styled to look like desktop application buttons, trees, and tables. The right answer to this conundrum is still being worked out by webmasters, usability gurus, and everyday users of the Web as it continues to evolve. In the meantime, the best advice available is to keep things consistent. If one part of your application uses web-style single clicks to launch pop-up windows, and another part requires double-clicks on similar-looking icons, your user will quickly become confused. And if you must have a talking pig that guides your users around the site, make sure that it doesn't suddenly change its accent, costume, or hairstyle halfway through!
From the point of view of your codebase, consistency and reuse go hand in hand. If you cut and paste functionality from one location to another, and then respond to a change request in three copies of the button-rendering code but miss a fourth, the consistency of your interface will erode over time. If there is only one copy of the button-rendering code that everyone uses, then the consistency of your application is likely to remain high. This applies not only to visual UI behavior but also to less-visible parts of the interface, such as network timeouts and responses to bad data.
Created: March 27, 2003
Revised: October 31, 2005