Highly usable systems hide complex GIS operations from the user and get the desired answer quickly. in the page, and it is a critical usability feature that is often overlooked. Hold the user's hand and they will love you for it. Lesson 3: Reassure the User When GIS professionals execute an attribute query or run an intersect operation, they typically understand that sometimes the resulting set is empty. Non-GIS users get very nervous when they perform an action and are presented with an empty user interface or are redirected to something they didn't expect. Did they delete something important? Is the request still processing? Did the site crash? What happened to the data? The importance of reassuring the user anytime something out of the ordinary happens cannot be overstated. Continuing with the roadway manager example, Figure 3 illustrates a case in which the roadway manager has selected a project with no location information. Rather than showing her an empty interface and having her worry about what has happened, the map interface is zoomed to the general area of the project (indicated by the text under Location Map). An information dialog box explains that there is no need to worry and provides instructions on how to remedy the missing data issue. There is no need for a complicated exception or null case scenario. A simple modal dialog box addresses the usability issue and keeps the user on the right track. Lesson 4: Protect Users from Themselves Despite a developer's best efforts, users can do strange and unexpected things with the systems. This is precisely why focused apps that support constrained workflows are critical. If a user continually finds it easy or convenient to circumvent application logic or generate bad data, this will impact the utility of the application and affect the willingness of a user or an organization to use the app. In Figure 4, the roadway manager is specifying the begin point of her roadway resurfacing project by clicking on a point along a road in the map. Note that she has clicked a point Continued on page 28 ArcUser Fall 2009 27 Figure 2: Use simple static content and dynamic feedback to lead the user through the application. Lesson 2: Provide Your Users with Feedback Nothing presents a bigger usability hurdle than a mapping application that leaves the user wondering, Well this looks cool, but what do I do? This is the principal downfall of applications that try to shove GIS into a Web browser. Geodevelopers know exactly what to do with three different toolbars and four menus containing all manner of map navigation, query, buffer, and analysis tools. Line-of-business users and the public find open workflow applications with no guidance intimidating. The Web mapping industry at large must learn to develop applications that satisfy specific workflows and lead users through those workflows in the www.esri.com application with visual cues and feedback in the user interface. The roadway manager introduced in Lesson 1 uses the interface in Figure 2 to specify the begin and endpoints of a roadway project. First, note the simple information panels that appear in the right-hand column of the site. They explain how to use the features on the page. Second, accept that while a GIS professional knows that clicking a pencil icon will let them draw something on a map, a roadway manager does not necessarily connect these two actions. (Click the map to set the begin point.) For our roadway manager, clicking the pencil icon causes information to appear below the map telling her what to do next. It's as simple as showing or hiding a