What are robustness principles for usability?

Usability is a quality of the user interface that indicates how easily and efficiently a user can perform a task using it. There are some principles that designers should incorporate into their design to maximize usability. These principles are divided into three broad categories:

• Learnability

• Flexibility

• Robustness

In this answer, we will explain the robustness principles that support usability.

Robustness principles

Robustness is the ability of an interface to aid the successful accomplishment and evaluation of tasks. Explained below are the principles that concern robustness.

Observability

Observability refers to the ability of users to evaluate a system's internal state using the information displayed on the interface. Observability is related to the following five principles:

• Browsability: This allows users to investigate the system's internal state using the information displayed on the interface.

• Defaults: This refers to default values in input fields. Providing these reduces the user's memory and physical load and acts as an error prevention technique.

• Reachability: This is the possibility of navigating to other screens as perceived by the observable system state.

• Persistence: This refers to how long the effect of an action exists in the interface.

• Operation visibility: This principle allows users to predict which operations can or can not be performed on the interface.

An example of observability is when the interface displays the percentage of completion while a file is downloading, as shown below.

Recoverability

The principle of recoverability concerns the ability of users to reverse the effect of errors. There are two types of error recovery:

• Forward error recovery involves accepting and negotiating the error to achieve the desired state.

• Backward error recovery involves reversing the error using some undo functionality.

Recoverability is related to the principle of commensurate effort, which states that performing an action should be difficult if, once performed, reversing it would be difficult. For example, the delete option should be kept in a location that is difficult to reach by the user.

Responsiveness

Responsiveness refers to the response time taken by the system to communicate with the user. This principle says that the system should respond instantaneously or within a short time. For example, the interface should display the pull-down menu options as soon as a user clicks the mouse button.

However, sometimes, the action requested cannot be completed instantaneously. In such situations, the system should respond with some confirmation that the request has been received and is being processed. For example, when a user chooses to download a large file, the interface should display an appropriate message that the download may take a while.

Task conformance

Task conformance deals with the degree of support the system offers for task completion. It has the following two aspects:

• Task completeness: This means that the system should allow the execution of the task requested by the user.

• Task adequacy: This means that the required task should be supported in a way that the user wants and can understand.

To maximize task conformance, the features available in the interface should match those observed in the task analysisTask analysis is a phase of the UI design process in which the tasks are observed and assessed. while designing the interface.