Interaction principles include general design recommendations that are not tied to a specific system or context of use. In general, the interaction principles can overlap when it comes to a usability problem.

At the outset, it is important to note that the Interaction Principles are the revised version of the Dialogue Principles, as these were open to further development. For example, learnability was unnamed learnability, or the principle of customizability was subordinated to the principle of controllability.

A precise definition of the interaction principles can be found in the latest version (2020) of ISO 9241-112 and ISO 9241-125.

In the following the interaction principles are listed with suitable examples.

Task appropriateness
An interactive system is task-appropriate if it supports users in completing their tasks, i.e., if the operating functions and user-system interactions are based on the characteristic properties of the task (rather than on the technology used to complete the task).

Example: a parking ticket machine clearly indicates which credit cards are accepted.

Self-descriptiveness
Wherever necessary for the user, the interactive system provides appropriate information that makes the capabilities of the system and its use immediately obvious without requiring unnecessary user-system interactions.

Unnecessary user-system interactions include unnecessary trial and error or consultation of external sources of information.

Example: In a train station, electronic display devices show the time remaining until departure instead of the train departure times, so that the user does not have to determine the current time and then calculate the time still available to catch the train.

Conformity to expectations
The behavior of the interactive system is predictable based on the context of use and generally accepted conventions in that context.

Consistency fundamentally increases the predictability of an interaction.

Example: an online store for purchasing stamps allows the user to select the destination country and displays the required amount for which stamps must be purchased.

Learnability
The interactive system supports discovery of its capabilities and how to use them, allows exploration ("trial and error") of the interactive system, minimizes learning effort, and provides support when learning is required.

Discovery allows the user to build a mental model and mnemonic rules.

Example: the user is offered an introductory tour to learn how to use the interactive system, minimizing the need to consult a user manual.

Learnability
The interactive system supports discovery of its capabilities and how to use them, allows exploration ("trying out") of the interactive system, minimizes learning effort, and provides support when learning is required.

Discovery allows the user to build a mental model and mnemonic rules.

Example: the user is offered an introductory tour to learn how to use the interactive system, minimizing the need to consult a user manual.

Controllability
The interactive system allows the user to maintain control over the user interface and interactions, including the speed, sequence, and individualization of the user-system interaction.

While flexibility focuses on alternative options that the interactive system directly provides to the user to achieve a desired goal, customization focuses on the ability of the interactive system to be adapted by the user depending on individual knowledge, skills, and personal preferences.

For example, a virus program used to scan a hard disk drive for viruses can be interrupted at any point by the user clicking a clearly visible stop button.

Robustness against user errors
The interactive system assists the user in avoiding errors, tolerates user errors in the case of detectable errors, and assists the user in troubleshooting.

An interactive system provides fault tolerance when the intended result can be achieved with either no or minimal corrective effort on the part of the user, despite recognizably erroneous input.

For example, an insurance policy issuance system pre-fills all input fields for which data has been entered elsewhere in the system with data already known to the system, rather than requiring re-entry.

User engagement
The interactive system presents features and information in an inviting and motivating manner, encouraging continuous interaction with the system.

An interactive system with user engagement encourages users to use it longer and more frequently, to devote resources to it (cognitive, financial, human, etc.), and to choose it over other systems with similar functionality.

User retention can lead to a positive user experience.

Excessive or inappropriate use of user engagement techniques can lead to a negative user experience.

Example: an antivirus program displays the following clear confirmation: "You are protected," along with a big green checkmark and a "Learn more" link.

Now one or the other may ask: Aren't the interaction principles actually the same as the heuristics? You can find out exactly where the difference lies in our article: ...