User Guidance refers to the means available to advise, orient, inform, instruct, and guide the users throughout their interactions with a computer (messages, alarms,labels, etc.), including from a lexical point of view.
As it is used here, Prompting has a broader definition than usual. Here it refers to the means available in order to lead the users to making specific actions whether it be data entry or other tasks. This criterion also refers to all the means that help users to know the alternatives when several actions are possible depending on the contexts Prompting also concerns status information, that is information about the actual state or context of the system, as well as information concerning help facilities and their accessibility.
1.2. Grouping/Distinction of Items
The criterion Grouping/Distinction of Items concerns the visual organisation of information items in relation to one another. This criterion takes into account the topology (location) and some graphical characteristics (format) in order to indicate the relationships between the various items displayed, to indicate whether or not they be long to a given class, or else to indicate differences between classes. This criterion also concerns the organisation of items within a class.
1.2.1. Grouping/Distinction by Location
The criterion Grouping/Distinction by Location concerns the relative positioning of items in order to indicate whether or not they belong to a given class, or else to indicate differences between classes. This criterion also concerns the relative positioning of items within a class.
1.2.2. Grouping/Distinction by Format
The criterion Grouping/Distinction by Format concerns more precisely graphical features (format, colour, etc.) that indicate whether or not items belong to a given class, or that indicate distinctions between different classes, or else distinctions between items of a given class.
1.3. Immediate Feedback
Immediate Feedback concerns system responses to users’ actions. These actions may be simple keyed entries or more complex transactions such as stacked commands. In all cases computer responses must be provided, they should be fast, with appropriate and consistent timing for different types of transactions. In all cases, a fast response from the computer should be provided with information on the requested transaction and its result.
Legibility concerns the lexical characteristics of the information presented on the screen that may hamper or facilitate the reading of this information (character brightness, contrast between the letter and the background, font size, interword spacing, line spacing, paragraphs spacing, line length, etc.). By definition, the criterion Legibility does not concern feedback or error messages.
The criterion Workload concerns all interface elements that play a role in the reduction of the users’ perceptual or cognitive load, and in the increase of the dialogue efficiency.
The criterion Brevity concerns the perceptual and cognitive workload both for individual inputs and outputs, and for sets of inputs (i.e., sets of actions needed to accomplish a goal or a task). Brevity corresponds to the goal of limiting the reading and input workload and the number of action steps.
The system should almost disappear, be transparent, while used to allow users to focus on the activity and to engage in the experience.
2.1.2. Minimal Actions
The criterion Minimal Actions concern workload with respect to the number of actions necessary to accomplish a goal or a task. It is here a matter of limiting as much as possible the steps users must go through.
2.2. Information Density
The criterion Information Density concerns the users’ workload from a perceptual and cognitive point of view with regard to the whole set of information presented to the users rather than each individual element or item.
3. Explicit Control
The criterion Explicit Control concerns both the system processing of explicit user actions, and the control users have on the processing of their actions by the system.
3.1. Explicit User Action
The criterion Explicit User Action refers to the relationship between the computer processing and the actions of the users. This relationship must be explicit, i.e., the computer must process only those actions requested by the users and only when requested to do so.
3.2. User Control
The criterion User Control refers to the fact that the users should always be in control of the system processing (e.g., interrupt, cancel, pause and continue). Every possible action by a user should be anticipated and appropriate options should be provided.
The adaptability of a system refers to its capacity to behave contextually and according to the users’ needs and preferences.
The criterion Flexibility refers to the means available to the users to customise the interface in order to take into account their working strategies and/or their habits, and the task requirements. Flexibility is reflected in the number of possible ways of achieving a given goal. In other words, it is the capacity of the interface to adapt to the users’ particular needs.
4.2. User Experience
The criterion User Experience refers to the means available to take into account the level of user experience.
5. Error Management
The criterion Error Management refers to the means available to prevent or reduce errors and to recover from them when they occur. Errors are defined in this context as invalid data entry, invalid format for data entry, incorrect command syntax, etc.
5.1. Error Protection
The criterion Error Protection refers to the means available to detect and prevent data entry errors, command errors, or actions with destructive consequences.
5.2. Quality of Error Messages
The criterion Quality of Error Messages refers to the phrasing and the content of error messages, that is: their relevance, readability, and specificity about the nature of the errors (syntax, format, etc.) and the actions needed to correct them.
5.3. Error Correction
The criterion Error Correction refers to the means available to the users to correct their errors.
The criterion Consistency refers to the way interface design choices (codes, naming, formats, procedures, etc.) are maintained in similar contexts, and are different when applied to different contexts.
7. Significance of Codes
The criterion Significance of Codes qualifies the relationship between a term and/or a sign and its reference. Codes and names are significant to the users when there is a strong semantic relationship between such codes and the items or actions they refer to.
The criterion Compatibility refers to the match between users’ characteristics (memory, perceptions, customs, skills, age, expectations, etc.) and task characteristics on the one hand, and the organisation of the output, input, and dialogue for a given application, on the other hand. The criterion Compatibility also concerns the coherence between environments and between applications.