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Subject : HCI
Semester : V
By: Arpit Kumar Sharma
Assistant Professor
ARYA Institute of Engg. Tech. & Management
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Contents :
1. Shneiderman’s Eight Golden Rules
2. Norman's 7 Principles
3. Norman’s Interaction Theory
4. 10 Usability Heuristics for User Interface Design /
(Nilsen’s ten heuristics Rules)
5. Contextual inquiry
6. Cognitive walk through
3. 1. Shneiderman’s Eight Golden Rules :
Ben Shneiderman (born August 21, 1947)
is an American computer scientist and
professor at the University of Maryland
Human-Computer Interaction Lab. His work
is comparable to other contemporary
design thinkers like Don Norman and
Jakob Nielsen.
In his popular book "Designing the User
Interface: Strategies for Effective Human-
Computer Interaction",
Shneiderman reveals his eight golden
rules of interface design:
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4. 1 Strive for consistency.
Consistent sequences of actions should be required in similar situations; identical
terminology should be used in prompts, menus, and help screens; and consistent commands
should be employed throughout.
2 Enable frequent users to use shortcuts.
As the frequency of use increases, so do the user's desires to reduce the number of
interactions and to increase the pace of interaction. Abbreviations, function keys, hidden
commands, and macro facilities are very helpful to an expert user.
3 Offer informative feedback.
For every operator action, there should be some system feedback. For frequent and minor
actions, the response can be modest, while for infrequent and major actions, the response
should be more substantial.
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5. 4 Design dialog to yield closure.
Sequences of actions should be organized into groups with a beginning, middle, and end.
The informative feedback at the completion of a group of actions gives the operators the
satisfaction of accomplishment, a sense of relief, the signal to drop contingency plans and
options from their minds, and an indication that the way is clear to prepare for the next
group of actions.
5 Offer simple error handling.
As much as possible, design the system so the user cannot make a serious error. If an error
is made, the system should be able to detect the error and offer simple, comprehensible
mechanisms for handling the error.
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6. 6 Permit easy reversal of actions.
This feature relieves anxiety, since the user knows that errors can be undone; it thus encourages
exploration of unfamiliar options. The units of reversibility may be a single action, a data entry,
or a complete group of actions.
7 Support internal locus of control.
Experienced operators strongly desire the sense that they are in charge of the system and that
the system responds to their actions. Design the system to make users the initiators of actions
rather than the responders.
8 Reduce short-term memory load.
The limitation of human information processing in short-term memory requires that displays be
kept simple, multiple page displays be consolidated, window-motion frequency be reduced, and
sufficient training time be allotted for codes, mnemonics, and sequences of actions.
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7. 1. Use both knowledge in the world and knowledge in the head.
2. Simplify the structure of tasks.
3. Make things visible: bridge the gulfs of Execution and Evaluation.
4. Get the mappings right.
5. Exploit the power of constraints, both natural and artificial.
6. Design for error.
7. When all else fails, standardize.
2. Norman's 7 Principles : 7
8. 3. Norman’s Interaction Theory
An obvious diagram of the Human-Computer Interface interaction:
Human <—> Interface <—> Computer
The diagram does not illuminate much. Norman’s 1988 book the Design of
Everyday Things is one of the first appearance of the phase “user centered
design.” Norman’s genius was to view the interaction as a cycle with two
components; execution and evaluation:
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9. Viewing the HCI as cycle is an accurate representation with respect to both the user and the
system (computer and program) point of views. Execution and evaluation are words the user
understands. According to Norman the execution component can be further divided into:
1.Establishing the goal
2.Forming the intention
3.Specifying the action sequence
4.Executing the action
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10. The evaluation component is divided into:
1.Perceiving the system state
2.Interpreting the system state
3.Evaluating the system state
From the user’s perspective, the user first establishes a vague goal which the user specifies by forming an
intent. Then the user can determine a sequence of actions that the user executes. After the system responds (or
maybe before if the system is slow), the user perceives the new system state which the user interprets and
evaluates with respect to the user’s intended goal. The cycle repeats. The user forms the execution and
evaluation in a task domain, called the task language. The system responses to the user’s action in a different
language, called the core language. A major cause of HCI failure is the differences between the two
languages. Norman defines to kinds of errors due to the gulf of execution and the gulf of evaluation. A problem
with Norman’s model is that it does not make the UI explicit. Abowd and Beale (1991) extended making the
UI explicit. There are still two languages, task and core, but the UI is responsible for translation between
languages, so the gulfs exist in the UI. The UI is involved in 4 mappings:
1. Articulation
2.Performance
3.Presentation
4.Observation
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11. The picture I like to draw is two horse shoes, one representing the system
and the other the user. The gap between the horse shoes representing the
gulfs in the UI.
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12. HCI errors can be associated with the four mappings :
Articulation:
•Clustering of light switches in a room
•Adjacent keys causing opposite state changes
•Pressing keys simultaneously
Performance:
•To shut down Windows user must click on START
•User can not find important Windows OS commands
•Applications missing important utilities
•Applications performing the command wrong
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13. Presentation:
•Lack of indication, no visual change in the UI
•Netscape navigator status bar; document done
Observation:
•User falls asleep during boot up and misses important log information :)
•Can not read fonts
•Windows outside of the desktop view port or under other windows
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14. 4. 10 Usability Heuristics for User Interface Design /
Nilsen’s ten heuristics Rules :
#1: Visibility of system status
The system should always keep users informed about what is going on,
through appropriate feedback within reasonable time.
#2: Match between system and the real world
The system should speak the users' language, with words, phrases
and concepts familiar to the user, rather than system-oriented terms.
Follow real-world conventions, making information appear in a
natural and logical order.
#3: User control and freedom
Users often choose system functions by mistake and will need a
clearly marked "emergency exit" to leave the unwanted state without
having to go through an extended dialogue. Support undo and redo.
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15. #4: Consistency and standards
Users should not have to wonder whether different words,
situations, or actions mean the same thing. Follow platform
conventions.
#5: Error prevention
Even better than good error messages is a careful design which
prevents a problem from occurring in the first place. Either eliminate
error-prone conditions or check for them and present users with a
confirmation option before they commit to the action.
#6: Recognition rather than recall
Minimize the user's memory load by making objects, actions, and
options visible. The user should not have to remember information
from one part of the dialogue to another. Instructions for use of the
system should be visible or easily retrievable whenever appropriate.
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16. #7: Flexibility and efficiency of use
Accelerators — unseen by the novice user — may often speed up the interaction for the
expert user such that the system can cater to both inexperienced and experienced users.
Allow users to tailor frequent actions.
#8: Aesthetic and minimalist design
Dialogues should not contain information which is irrelevant or rarely needed. Every extra
unit of information in a dialogue competes with the relevant units of information and
diminishes their relative visibility.
#9: Help users recognize, diagnose, and recover from errors
Error messages should be expressed in plain language (no codes), precisely indicate the
problem, and constructively suggest a solution.
#10: Help and documentation
Even though it is better if the system can be used without documentation, it may be necessary to
provide help and documentation. Any such information should be easy to search, focused on the
user's task, list concrete steps to be carried out, and not be too large.
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17. Contextual inquiry (CI) is a user-centered design (UCD) research method, part
of the contextual design methodology. A contextual inquiry interview is usually
structured as an approximately two-hour, one-on-one interaction in which the
researcher watches the user in the course of the user's normal activities and
discusses those activities with the user.
175. Contextual inquiry (CI) :
18. Contextual inquiry defines four principles to guide the interaction:
•Context—Interviews are conducted in the user's actual workplace. The researcher
watches users do their own work tasks and discusses any artifacts they generate or use
with them. In addition, the researcher gathers detailed re-tellings of specific past events
when they are relevant to the project focus.
•Partnership—User and researcher collaborate to understand the user's work. The
interview alternates between observing the user as he or she works and discussing what
the user did and why.
•Interpretation—The researcher shares interpretations and insights with the user during
the interview. The user may expand or correct the researcher's understanding.
•Focus—The researcher steers the interaction towards topics which are relevant to the
team's scope.
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19. 6. Cognitive walk through :
Cognitive walkthrough is a method of evaluating the user interaction of a working
prototype or final product. It is used to evaluate the system's ease of learning.
Cognitive walk through is useful to understand the user's thought processes and
decision making when interacting with a system, specially for first-time or
infrequent users.
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