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Prototyping Approaches

Table 7.1 summarizes five different prototyping approaches, from low-fidelity paper prototypes to the iPhone SDK. As the iPhone app space continues to evolve, you may find other approaches well suited to your application space. Be creative—adapt these as needed and formulate your own prototyping strategy. For example, audio can be incorporated into all of the options via a recording or live voice-over.

Table 7.1. Alternative iPhone App Prototyping Approaches





Cheap and fast. Good for identifying conceptual, flow, and terminology issues.

Difficult to show low-level interactions; harder to simulate information-rich apps.

Static images on device

Incorporates iPhone form factor. Good for addressing visual issues, e.g., text size.

Limited interaction possible; essentially click through screen to screen.

Interactive on device

Incorporates iPhone form factor and some level of interactivity.

Achieving desired interactivity can require a significant amount of time.


Storytelling approach that provides contextual information essential for location-aware and some immersive apps.

Can be time-consuming if many iterations are needed. Less suitable for usability testing.

iPhone SDK

Code may sometimes be used for the final app design.

Can be costly and less malleable for up-front iterative design.

Paper Prototypes

Paper prototypes are essentially paper models of your iPhone apps (Figures 7.37.4). They can be used as a communication tool, but they are often developed for usability testing. In these situations the designer or developer plays "computer," hiding and showing user interface elements as needed. In contrast to electronic prototypes, Jared Spool, the founder of User Interface Engineering, describes paper prototypes the following way: 8

Figures 7.3

Figure 7.3 Paper prototype of a ride-sharing iPhone app

Figures 7.4

Figure 7.4 Paper prototype of an iPhone with the Home screen

  • We think of paper prototyping as the coarse-grain sandpaper and electronic-version testing as the fine grain. Once we've used the paper prototypes to validate what each screen contains and how it will work, we then move over to the electronic version to fine-tune the look and feel.


The benefits of paper prototypes range from quick iterations to improved collaboration:

  • Quick iterations

    Paper prototypes enable you to rapidly iterate and experiment with many ideas. The modest time investment makes it easier to throw away less promising directions.

  • Inexpensive

    Ordinary office supplies can be used for paper prototypes: Sharpies, Post-its, printer paper. Most important, these up-front paper iterations can reduce costly changes on the development end.

  • Collaborative

    Paper prototypes do not require any technical skills; thus everyone (users, too!) can participate.

  • Easy to edit

    You or your users can edit paper prototypes on the fly (e.g., change labels, add screens, add buttons).

Issues to Explore

User experience issues often explored with paper prototypes include

  • App concept

    Do users understand your app's central concept?

  • Workflows

    Is the overall navigation clear? Are there too many steps to complete tasks?

  • Information organization

    Does the current organization match users' expectations?

  • Terminology

    Are the labels on tabs, screens, and buttons clear?

  • Additional features

    Over the course of evaluating your app, you may uncover additional features that users need. Users may vocalize these needs, or you may observe them trying to complete tasks not supported in the app. You may also learn which features users don't want, which could save valuable development time.


As mentioned previously, paper prototypes are less suitable for refining low-level interactions such as transitions, scrolling, and swiping. They may also be less useful for certain classes of apps, such as musical instruments, videos, and games.

How to Do It

iPhone paper prototypes typically include the "device" and some combination of screens, overlays, and controls. Steps for creating paper prototypes are summarized in this section.

  • Step 1: Gather materials.

    In the previous chapter we listed office supplies that can be used when brainstorming and sketching your app designs; these items are also useful for paper prototyping. In addition, you may want to have the following materials on hand: cardboard, removable tape, glue, correction fluid, and scissors.

  • Step 2: Determine the form factor.

    At some point your designs will have to match the iPhone screen dimensions—320 x 480 pixels (640 x 960 for iPhone 4)—but paper prototypes can be less exact. Using a larger form factor will make it easier for others to interact with the design (e.g., rearrange the layout and write in text fields).

  • Step 3: Create the prototype.

    Your prototype will include a background, the screens, and the user interface controls. As you create the prototype, be sure your scenarios, as discussed in Chapter 4, and application flowchart are readily available.


If your prototype is much larger than the iPhone, you may want to frame your designs with a cutout iPhone made with foam core or cardboard. This frame can help orient participants when usability-testing your app. Alternatively, if your prototype matches the iPhone dimensions, you can adhere it to the device, potentially making it "feel" closer to the real thing.


Your app screens can be hand-drawn or screenshots. Hand-drawn sketches tend to elicit high-level conceptual feedback, whereas screenshots may lead to low-level visual feedback. If possible, stick with one approach, not half hand-drawn screens and half screenshots. A few notable exceptions are photos, maps, and keyboards: Printing these out will save time, and they'll work fine when combined with hand-drawn sketches.

Prepare the Controls

This section includes tips on building standard controls for your paper prototype.

  • Tab bar

    Create highlighted and non-highlighted versions of tab states (Figure 7.5). Use text if you haven't decided on the appropriate tab icon.

    Figures 7.5

    Figure 7.5 Paper prototype with a tab bar

  • Keyboard

    As mentioned earlier, you can use hand-drawn keyboard sketches or screenshots (Figure 7.6). It's not necessary to have the pressed state for each button, but pay attention to the default colors and special contextual keys such as those for web and email addresses.

    Figures 7.6

    Figure 7.6 Sample sketch with a keyboard printout

  • Sliders

    Sliders can be created with a tiny piece of construction paper folded over a narrow strip of paper (Figure 7.7). If you're short on time, you can provide verbal feedback as the user moves a finger back and forth across the slider. This verbal approach can also be applied to progress bars (e.g., "Downloading 1 of 10").

    Figures 7.7

    Figure 7.7 Example of a slider

  • Text entry

    For text entry, participants can write on Post-its or removable tape. Alternatively, they can use a pencil to write directly on the prototype. Be forewarned: Even with good erasing, if participants write too hard, your next user may see what the previous one wrote.

  • Pickers

    Pickers provide essentially the same function as drop-down lists on web or desktop applications (Figure 7.8). Given that they can include a large number of items, you may need a long strip of paper to display all of the options. The strip can be folded and tucked away when the user is not interacting with the picker.

    Figures 7.8

    Figure 7.8 Example of a time picker

  • Highlight

    Consider creating a highlight cutout that you can move up or down as the user makes selections (Figure 7.9). Another option is to buy transparent plastic sheets, which come in a variety of colors.

    Figures 7.9

    Figure 7.9 Example of a highlight

  • Alerts

    Consider using a different background color for your alerts. Make sure they don't completely obscure content that should be visible underneath (Figure 7.10).

    Figures 7.10

    Figure 7.10 Example of an alert overlay

  • Segmented controls

    Include different states of segmented controls, which are typically used for filters or sorts. Each state can show a different "segment" of the control highlighted. The segmented control in Figure 7.11 lets users sort the list by Popularity, Rating, and Title.

    Figures 7.11

    Figure 7.11 Segmented control example

Here are some additional elements you may need to include:

  • Loading page indicator
  • On/off versions for switches that work like radio buttons
  • Check mark for selected items

Static Images on the Device

Once you have refined your overall concept and flows, you may want to create screen captures of your designs and display them on the iPhone. If you link the images with "hot spots," you can offer a more exploratory user experience since no one needs to play the role of "computer" while switching out user interface elements. Moreover, the precise form factor may make it easier to refine visual design details such as type size, layout, and color.

How to Do It

To start, you'll want to create 320 x 480 images of your app screens. Many drawing programs have iPhone templates built into the software or available for download. Keep in mind that these templates do not have all of the user interface elements in the iPhone universe; developers often create controls that look and feel like standard controls, but they are actually custom-designed and custom-coded. If there's something you need that's not available, be prepared to sketch the desired solution. There are four drawing programs widely used by iPhone UI designers:

  • OmniGraffle (see Graffletopia, www.graffletopia.com, for iPhone templates)
  • Fireworks
  • Photoshop
  • Illustrator

I prefer OmniGraffle and Fireworks since the "page" framework translates well to iPhone screen design. Photoshop and Illustrator are excellent products, but the number of tools and options tends to overwhelm novice users. Three easy ways to view images on the iPhone are via the built-in slideshow, Safari, and LiveView.

Viewing via Built-in Slideshow

The downsides of the slideshow approach are the linearity—you can only swipe forward or back—and the presence of zoom and slideshow controls. On the plus side are speed and simplicity: Save your sketches in an acceptable iPhoto format, then add them to your iPhone photo collection. Be sure to include the status bar (battery and connection information) if it is part of your design.

Viewing via Safari

Another option is to create images with "hot spots" and display these images in Safari. With this approach, users can tap on rows and buttons just as they would with a real app. UNITiD design put together some scripts that enable you to disable zoom and view the images in full-screen mode. An easy-to-follow tutorial can be found on their web site. 9


LiveView, 10 created at IDEO Labs, allows you to view desktop designs from your iPhone (Figure 7.12). This can help you evaluate the app layout, type sizes, and other visual elements, but it's not possible to interact with the prototype. Additionally, LiveView must be accessed over WiFi, so the geographical range of your testing may be limited.

Figures 7.12

Figure 7.12 iPhone app viewed via LiveView, which was developed at IDEO

Interactive on the Device

Given the limitations of static image prototypes, you may prefer more interactive prototyping techniques. Before choosing this route, make sure you've evaluated all of the lower-fidelity options. If some aspects of your app, such as flows and layout, can be worked out on paper, start with paper before committing to an interactive prototype. I'm deliberately using the word committing because higher-fidelity prototypes have a tendency to become final designs.

Issues to Explore

You can explore almost any aspect of the user experience; it basically depends on how much time you want to put into the prototype. In contrast to static image prototypes, you can provide forms, transitions, and scrolling content. More important, given the portability of these prototypes, you can get out in the field and walk through your scenarios in context. Although this can be done with paper, the process is much easier with an interactive prototype on the device.


Although interactive prototypes are powerful, there are still some aspects that differentiate them from the "real" experience. In particular, you will still likely need to fake the current location information, live data feeds, and the handling of interruptions (what happens when the connection is lost or disrupted?).

How to Do It

Interactive prototypes can be created with tools like Keynote or PowerPoint 11 (Figure 7.13), but specialized readers are required to display these on the iPhone. 12 On the other end of the spectrum are custom CSS solutions that are essentially web applications made to look like native iPhone applications. These prototypes can take a significant amount of time, though there are some tools like ProtoShare (Figure 7.14) that aim to simplify the process. 13 Another solution that holds promise is Briefs, developed by Rob Rhyne. 14 Briefs prototypes run on the iPhone, like actual apps, but take much less time to code and produce. Each "brief" contains a text file that references a series of static images organized into "scenes."

Figures 7.13

Figure 7.13 MockApp example of Google Wave

Figures 7.14

Figure 7.14 ProtoShare example showing cover flow

Video Prototypes

Video prototypes are a powerful way to show app usage in context—the actors, the environment, concurrent activities, the passage of time. These contextual elements are particularly important for apps that interact with the real world: location-aware apps, remote controls, cooking aids. Additionally, immersive apps such as musical instruments or games may use video to show their apps in action. Although video prototypes can be used to elicit feedback via usability testing, they are typically created to evaluate and communicate design ideas. Figure 7.15 shows a screen capture from a video prototype created for a caregiver app; the full video is available online. 16

Figures 7.15

Figure 7.15 Prototype of Eldia app for caregivers

Issues to Explore

Video prototypes are an effective way to explore and document how an app works in the real world. Examples of interactions that may be captured include

  • Handling of the device while performing other activities
  • Other people who impact the experience
  • Interruptions that may influence the user

Harder to Explore

Some issues are less suitable for a video prototype. For example, if you want to explore low-level interactions in great detail, consider creating an interactive proto type that users can walk through at their own pace.

How to Do It

Video prototypes may seem like a significant undertaking, but the process can be relatively simple:

  • Step 1. Develop your script.

    First, you'll want to develop a script for your video. If you created scenarios as discussed in Chapter 4, it shouldn't take long to write the script. Focus on the scenarios that show how the app is used in a contextual and realistic way. Also, include an introduction to set the stage, for example, who the characters are, where are they located, what their goals are.

  • Step 2. Sketch storyboards.

    If you have already created storyboards for your app, you'll want to adapt them based on your script. You may discover that additional screens are needed to provide a seamless user experience.

  • Step 3. Create your prototype.

    Your prototype can be paper, electronic, or whichever medium you find most effective. Be sure your screens, overlays, and so on are ready before you start shooting video.

  • Step 4. Film your prototype.

    You don't need to purchase an expensive high-end camera to film your prototype. At a minimum, be sure your camera has solid zoom capabilities and a good microphone. If the microphone picks up too much background noise, you may want to rent or purchase a lavalier microphone that can be clipped onto the actor's shirt. Here are some additional video tips:

    • Choose realistic locations; seek permission to shoot video as needed.
    • Ask the main actor to "think aloud" so viewers know the "whys" behind his or her actions.
    • Use a combination of environmental views and close-up app screen views.
  • Step 5. Edit your video.

    There are dozens of video-editing tools on the market. For the purposes of your video prototype, something basic such as iMovie should be sufficient. Some additional editing tips are the following:

    • If background information is necessary, remember to start with a voice-over to set the stage.
    • Try to keep the final video under five minutes.
    • Use fade in/out to indicate the passage of time.

Other Types of Video Prototypes

As mentioned in the previous section, video prototypes can also be an effective way to illustrate how immersive apps like games and musical instruments work. Gogogic, an online and iPhone game developer, uses animatics in its app development process. Animatics,17 a series of still images displayed in sequence, enable Gogogic to visualize the player experience before diving into coding. Additionally, animatics help prioritize the app requirements. According to Gogogic's CEO, Jónas Antonsson, "At Gogogic, the animatic is king" (Figure 7.16).

Figures 7.16

Figure 7.16 Animatics Gogogic developed for the game Symbol6


Another approach is to animate your scenario with cartoon-like characters as is done with the Xsights iPhone app (Figure 7.17). Services like GoAnimate provide tools and templates to help newbies create basic animations.

Figures 7.17

Figure 7.17 Animation developed for Xsights app


The iPhone SDK

Prototypes can be developed using the iPhone SDK within Interface Builder. While some design professionals may argue that "working code" is not prototyping, it really depends on the domain and the prototype complexity. For example, paper prototyping would be inadequate for exploring a musical instrument app. In this case, digging into Apple's Audio Library may be the most efficient way to experiment and figure out what's possible.

Almost any aspect of the user experience can be explored, but be careful how far you develop your prototype—if you become too invested in the design, you may be less likely to adapt it based on user feedback. Also, if your prototype isn't fully functioning, it will still be challenging to evaluate features such as location awareness and live data feeds.

How to Do It

Programming the iPhone user experience is too broad a topic to cover in this book. There are countless books and web sites on the topic. Some titles in the Addison-Wesley family that have been well received include

  • Cocoa Programming for Mac OS X, Third Edition, by Aaron Hillegass (2008)
  • The iPhone Developer's Cookbook: Building Applications with the iPhone 3.0 SDK, Second Edition, by Erica Sadun (2009)

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