As designers, how can we determine whether the design we create is usable by the user? Design guidelines and principles are required to assess the usability of the design. In human-computer interaction (HCI), we classify the principles that assist usability into three categories:
Learnability
Robustness
In this Answer, let's discuss robustness in detail.
A user interacts with a computer in a work or task domain to accomplish a specific set of objectives. The robustness of that interaction includes features that facilitate the effective accomplishment and evaluation of the goals.
Robustness is the degree of assistance offered to the user in assessing goal-directed behavior and successfully identifying system performance in terms of interaction.
We can enhance the usability of an interactive system by applying the following defined robustness principles to the system design:
Observability
Recoverability
Responsiveness
Task conformance
Observability enables the user to evaluate the system's internal status through its visual representation at the interface.
For example, the system displays the downloading file status on the interface as follows:
Users often make mistakes from which they desire to recover. Recoverability is the ability to achieve the desired goal after recognizing an error in a previous interaction. Recovery can occur in one of two directions: forward or backward.
Forward error recovery entails accepting the present state and negotiating from it to the desired state. If we cannot undo the impact of the interaction, forward error recovery may be our sole option for recovery. For example, deleting a file permanently by mistake is forward recoverability. That is, we cannot undo the effect of this misfortune except by redownloading the file.
Backward error recovery is an attempt to reverse the effects of previous interactions to return to a prior state before proceeding. For example, in a text editor, a mistyped keystroke may erase a significant section of text that we would like to recover using an equally simple undo button.
The communication rate between the system and the user is measured as responsiveness. Response time is commonly described as the amount of time the system requires to communicate state changes to the user. In general, users prefer short durations and prompt responses. Even if there is no instantaneous response, the user must be informed that the system has received the request for action and is working on a response.
For instance, we require pull-down menus to appear instantly when we press a mouse button.
The goal of an interactive system is to allow a user to execute various tasks to achieve specific objectives within a particular application domain. Task conformance addresses whether the system supports all of the actions of interest, and whether it supports these in the manner the user desires. Two aspects of task conformance are defined as follows:
Task completeness: This is the degree to which the system services can be mapped onto all user tasks. For example, Google Docs provides all of the operations that a user may potentially execute while creating a text document.
Task adequacy: This is the system considering the user's understanding of the tasks and supporting tasks in the intended direction. For example, Google Docs offers to upload an image from the dropdown menu, but not all options are available in that menu. What if the user has to select from the drive? They cannot directly choose that option.
Overall, robustness ensures that the user can always recover from errors. The notion of consistency assists users in learning the system and avoiding errors.
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