Degree to which a product or system can be interacted with by specified users to exchange information ia the user interfaceto complete specific tasks in a variety of contexts of use. This characteristic is composed of the following sub-characteristics:
- Appropriateness recognizability - Degree to which users can recognize whether a product or system is appropriate for their needs.
- Learnability - Degree to which the functions of a product or system can be learnt to be used by specified users within a specified amount of time.
- Operability - Degree to which a product or system has attributes that make it easy to operate and control.
- User error protection. Degree to which a system prevents users against operation errors.
- User engagement - Degree to which a user interface presents functions and information in an inviting and motivating manner encouraging continued interaction.
- Inclusivity - Degree to which a product or system can be used by people of various backgrounds (such as people of various ages, abilities, cultures, ethnicities, languages, genders, economic situations, etc.).
- User assistance - Degree to which a product can be used by people with the widest range of characteristics and capabilities to achieve specified goals in a specified context of use.
- Self-descriptiveness - Degree to wich a product presents appropriate information, where needed by the user, to make its capabilities and use immediately obvious to the user without excessive interactions with a product or other resources (such as user documentation, help desks or other users).