Definition of Guideline-Based Metrics to Evaluate AAL Ecosystem’s Usability

Table 6

Weinschenk and Barker’s cognitive principles of parametrization [156–161].

Principle	Type	Parameters
1	AO	Ensuring action reversibility; providing a task’s completion rate and a confirmation dialogue during the actions execution.
1	SeO	Including a clear indication of the current section; providing a global navigation menu.
2	AO	Ensuring interface response time lower than 10 s; providing stateful component’s capable of giving feedback to the user whenever a certain action is performed. For example, when the user clicks a hyperlink, the colour of the link should change to give awareness that the link was previously accessed.
2	SeO	Providing text content in a simple and direct manner; avoiding flourished font families and redundant hyperlinks; avoiding the use of unrelated images within the section’s context.
5	CO	Including hints to identify the data type accepted by the input component displayed, tooltips with the description of the component’s action, and labels/icons that clarify the component’s action purpose; avoiding the use of foreign words or acronyms in the text content provided; avoiding spelling errors.
6	CO	Ensuring aesthetic similarity, proximity, and continuity across components from the same family or used to perform a similar action.
7	CO	Providing default in the multiple-choice fields.
7	SeO	Providing mechanisms to display in a gradual fashion the interface functionalities, from a basic to an advanced setting.
8	CO	Ensuring the component’s consistency.
8	SeO	Including a clear indication of the current section and its hierarchical position within the interface structure using breadcrumbs; providing a global navigation menu.
9	SeO	Including mechanisms to predict the user’s intents.
11	SeO	Presenting trustworthy information according to the domain being modelled by the interface.
12	SeO	Providing mechanisms which allow the user to customize the interface look and feel to best fit his/her personal preferences.
18	AO	Ensuring that results/feedback provided matches user’s expectations.
19	AO	Providing mechanisms that allow for reversion/recovery from any action executed within the interface.

Notes: 1: user control; 2: human limitations; 5: linguistic clarity; 6: aesthetic integrity; 7: simplicity; 8: predictability; 9: interpretation; 11: technical clarity; 12: flexibility; 18: precision; 19: forgiveness.