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Given this application starts by going right to the camera, the user will not know exactly what to do at first. Only after taking a random picture and going through the process will the user figure out how the application works. This detracts from the initial efficiency of learning the application, because there are no blatant instructions for the user to read. In the long run, the user does not have to bypass a start screen or instruction screen that tells the user what it already knows. The application efficiently starts right out with a camera. After taking a picture, the user can touch randomly to learn exactly how to specify which object they are interested in. After specifying, the application reinforces exactly how to take pictures of object and annotate by allowing the simple process to be repeated. This also gives the user practice. Selecting which objects to review is fairly easy to learn. The pictures selected will highlight in some way to show the user exactly what is selected. The arrows on the shopping cart are very good affordances that indicate more details. In all, the learnability of this design is fairly good. It allows the user to play on their own and its not too verbose.
Safety
Since the efficiency of iPhone applications is very good, the user can correct an issue fairly quickly by hitting the back button to move up the screen hierarchy. Software architecture on the iPhone make this ability very easy to implement and allows the user for efficient error correction. The user cannot modify information displayed about the objects, separating the backend model from the user model. To the user, the application merely allows a way to quickly look up products for a simple way of comparing specifics.
Design B
This time, Sally can collect information about all the products she’s interested in more quickly by taking pictures that each have multiple bicycles in them:
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