Specifications

11 | USER INTERFACE
DESIGN GUIDE
Interaction diagrams visualize the sequence of activities within an interface. The flow of actions needed to perform specific
tasks is documented to ensure all needed functions are made available within the interface. Interaction diagrams are
specifically helpful for complex tasks which require multiple actions to complete. Creating them is a key to catching interface
errors early in the design process.
Usability Assessment in the Design Process
As described previously, usability testing is a key part of the design process. Usability assessment should begin early in the
development, when you still have the opportunity to make changes. You then incorporate your findings into the design
process. As the design progresses, usability assessment continues to provide valuable input for analyzing initial design
concepts and, in the later stages of interface design, can be used to test specific tasks. Make sure you allocate adequate
time in your schedule to address the issues that may arise from usability review. Don’t assume that the results will always
confirm your design. How you respond to what assessment reveals determines its value. When you are working through
details of individual features, don’t neglect to evaluate how these integrate into the design. The usability assessment should
include all of the interface’s components. Consider the user’s entire experience as part of the usability assessment. To help
ensure overall usability, define a list of the top twenty most important and frequent tasks users should be able to do, then
test all of these tasks regularly.
Navigation
Visual design serves a purpose greater than decoration; it is an important tool for effective communication. The organization
of information on the screen can make the difference between a message users understand and one that leaves users
feeling overwhelmed. Even the best interface can suffer and be underused if the visual presentation does not communicate
it well. It is important to understand how we function in the real world and interpret it correctly for touch panel interfaces.
For example, we read a screen in the same way we read other forms of information, left to right and top to bottom. The eye
is always attracted to colored elements before black-and-white elements, to isolated elements before elements in a group
and to graphics before text. We even read text by scanning the shapes of groups of letters. Consider the following principles
when you design the organization and composition of visual elements.
Hierarchy of Information
The principle of hierarchy of information addresses the placement of information based on its relative importance to