Design Rules for Interactive System
Principles of Learnability.
Learnability is a quality of products and interfaces that allows users to quickly become familiar with them and able to make good use of all their features and capabilities. Learnability is one component of usability and is often heard in the context of the user interface or user experience (UX) design, as well as usability and user acceptance testing.
1.Predictability
It determines the effect of future actions based on past interaction history as well as shows operation visibility.
2. Synthesizability
This is assessing the effect of past actions which are immediate vs eventual.
3.Familiarity
This implies that how prior knowledge applies to new system and the guessability..
4.Generalizability
This means extending specific interaction knowledge to new situations.
5.Consistency
In this principle, it implies that how likeness in input/output behavior arising from similar situations or task objectives.
Principles of 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. In other words it implies that the multiplicity of ways the user and system exchange information.
1.Dialogue initiative
It consider the freedom from system imposed constraints on input dialogue.There are two ways todata initiative. one is user preemptiveness which is user user initiates dialog.The next thing is system preemptiveness which is the system initiates dialog.
2.Multithreading
The ability of the system to support user interaction for several tasks at a time .There are two types of approches related to this. First one is concurrent multimodality which is simultaneous communication of information pertaining to separate tasks for example multi-model dialog, editing text and beep (incoming mail) at the same time. The secon approch is interleaving multimodality which permits temporal overlap between separate tasks dialog is restricted to a single task for example in window system, the window is a task,modal dialogs,interact with just one window at a given time.
3.Task migratability
In this principle it gives us access to pass responsibility for task execution between user and system. for example spell checking.
4.Substitutivity
This allows equivalent values of input and output to be substituted for each other representation.
5.Customizability
It gives us the modifiability of the user interface by the user (adaptability) or system (adaptivity).There are two approches in this principles.
adaptability: users ability to adjust the form of input and output
adaptivity: automatic customization of the user interface by the system
Principles of Robustness
1.Observability
Which is the ability of the user to evaluate the internal state of the system from its perceivable representation.
2.Recoverability
This implies the ability of the user to correct a recognized error.There are two approches in this case,
reachability (states): forward (redo) / backward (undo) recovery
commensurate effort : more effort / steps for deleting a file than for moving it.
3.Task conformance
This implies the degree to which system services support all of the user’s tasks.
4.Responsiveness
This discusse about how the user perceives the rate of communication with the system. Users preferred to short durations and instantaneous responses and stability and indication of response time.
Standards and Guideline for Interactive systems
Standards
Standards for interactive system design are usually set by national or international bodies to ensure compliance with a set of design rules by a large community. Standards can apply specifically to either the hardware or the software used to build the interactive system.
Guidelines
A Guideline is a rule about designing interactive systems.There are a vast number of published guidelines for interactive system design. Several books and technical reports contain huge catalogs of guidelines such as Google, Apple and etc.
Shneiderman’s Eight Golden Rules
1. Strive for consistency in action sequences, layout, terminology, command use and so on.
2. Enable frequent users to use shortcuts, such as abbreviations, special key sequences and macros, to perform regular, familiar actions more quickly.
3. Offer informative feedback for every user action, at a level appropriate to the magnitude of the action.
4. Design dialogs to yield closure so that the user knows when they have completed a task.
5. Offer error prevention and simple error handling so that, ideally, users are prevented from making mistakes and, if they do, they are offered clear and informative instructions to enable them to recover.
6. Permit easy reversal of actions in order to relieve anxiety and encourage exploration, since the user knows that he can always return to the previous state.
7. Support internal locus of control so that the user is in control of the system, which responds to his actions.
8. Reduce short-term memory load by keeping displays simple, consolidating multiple page displays and providing time for learning action sequences.
Norman’s Seven Principles
Norman’s seven principles also provide a summary of user-centered design philosophy.
1. Use both knowledge in the world and knowledge in the head. Systems should provide the necessary knowledge within the environment and their operation should be transparent to support the users
2. Simplify the structure of tasks. Tasks need to be simple in order to avoid complex problem solving and excessive memory load.
3. Make things visible. The interface should make clear what the system can do and how this is achieved, and should enable the user to see clearly the effect.
4. Get the mappings right User intentions should map clearly onto system controls and system events.
5. Exploit the power of constraints, both natural and artificial. Constraints are things in the world that make it impossible to do anything but the correct action in the correct way.
6. Design for error To err is human, so anticipate the errors the user could make and design recovery into the system.
7. When all else fails, standardize. If there are no natural mappings then arbitrary mappings should be standardized so that users only have to learn them once.
