Design rules for interactive systems
Learnability
Learnability principles are concerned with interactive system features, which aid novice users to learn quickly and also allows steady progression to expertise. There are five principles.
- Predictability - Support for the user to determine the effect of future action based on past interaction history.
- Synthesizability - Support for the user to assess the effect of past operations on the current state.
- Familiarity- The extent to which a user’s knowledge and experience in other real-world or computer-based domains can be applied when interacting with a new system.
- Generalizability - Support for the user to extend knowledge of specific interaction within and across applications to other similar situations.
- Consistency - Support for the user to extend knowledge of specific interaction within and across applications to other similar situations.
Flexibility
Flexibility in interactive design extends the way a user and the system exchange information. By applying flexibility principles to an interactive system design, designers aim to improve a system’s usability. There are five principles.
- Dialog initiative - User freedom from artificial constraints on the input dialog imposed by the system
- Multi-threading - The ability of the system to support user interaction for more than one task at a time.
- Task migratability- The ability to transfer control for execution of tasks between the system and the user ( e.g. spell-checking task).
- Substitutivity - The extent to which an application allows equivalent input and output values to be substituted for each other (values in input such as fractions/decimals, values in output eg both digital and analog, output/input eg output can be reused as input).
- Customizability - The ability of the user or the system to modify the user interface.
Robustness
Robustness is the level of support provided to the user in determining successful achievement and assessment of goals. It is the extent to which the user can reach the intended goal after recognizing an error in the previous interaction. There are four principles related to Robustness.
- Observability - The extent to which the user can evaluate the internal state of the system from the representation on the user interface.
- Recoverability - The extent to which the user can reach the intended goal after recognizing an error in the previous interaction.
- Responsiveness - A measure of the rate of communication between the user and the system.
- Task conformance - The extent to which the system services support all the tasks the user would wish to perform and in the way the user would wish to perform.
Standards and Guideline for Interactive systems
- Standards
Standards are set by national or international bodies to ensure compliance by a large community of designers to standardize the look and feel of a user interface and for a smooth HCI design process.
Ex: ISO Standards, National Standards provides by institutes like American National Standards Institute, British Standards Institution, Ente Nazoline Italiano Di Unificazoine
- Guidelines
Guidelines are more suggestive and general and there are many textbooks and reports full of guidelines.
Ex: Abstract guidelines applicable during early life cycle activities, Detailed guidelines (style guides) applicable during later life cycle activities, the Understanding justification for guidelines aids in resolving conflicts.
Shneiderman’s 8 Golden Rules
- Strive for consistency: layout, terminology, command usage, etc.
- Cater to universal usability - recognize the requirements of diverse users and technology. For instance add features for novices eg explanations, support expert users eg shortcuts.
- Offer informative feedback - for every user action, offer relevant feedback and information, keep the user appropriately informed, human-computer interaction.
- Design dialogs to yield closure - help the user know when they have completed a task.
- Offer error prevention and simple error handling - prevention and (clear and informative guidance to) recovery, error management.
- Permit easy reversal of actions - to relieve anxiety and encourage exploration, because the user knows she or he can always go back to previous states.
- Support internal locus of control - make the user feel that she or he is in control of the system, which responded to his or her instructions or commands.
- Reduce short-term memory load - make menus and UI elements/items visible, easily available, retrievable.
Norman’s 7 Principles
- Use both knowledges in the world and knowledge in the head.
- Simplify the structure of tasks.
- Make things visible: bridge the gulfs of Execution and Evaluation.
- Get the mappings right.
- Exploit the power of constraints, both natural and artificial.
- Design for error.
- When all else fails, standardize.
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