E3 Chap 01

UNDERSTAND HUMAN INTERACTION
Overview
Interaction models help to understand what is going
on in the interaction between user and system Ergonomics looks at the physical characteristics of the interaction and how these influence its effectiveness The dialogue between user and system is influenced by the style of the interface The interaction takes place within social and organizational context that affects both user and system
The Interaction
Refer to the communication between user and system Involved at least two participants:
a) User b) System
The Terms of Interaction

The purposes of interactive system - to aid a user accomplishing goals from some application domain Domain - an area of expertise and knowledge in some real-world activity - example: graphic design, authoring and process control in a factory Goal - The desired output from a performed task Task - Operation to manipulate the concepts of a domain Intention
- a specific action required to meet the goal
Example
One task within the graphic design domain is the
construction of a specific geometric shape with particular attributes on the drawing surface. A related goal would be to produce a solid triangle centered on the canvas.
Model of Interaction
Introduction
Human beings interact with a zillion devices and
systems everyday Designers of devices are constantly trying to understand what is it that makes the difference between devices, that are easy to use and those that are not? How should one design systems, that support easy user operation?
The Normans Execution-Evaluation cycle
The Normans Execution-Evaluation cycle: Simple Example

Intention: To switch on the desk lamp Sequence of action: to reach over and press the lamp switch / ask Execution: Execute the action Goal: To get light Evaluation: If enough light, then the cycle is complete Interpreting: If light is on then the lamp is ok Perceiving the result: Either the light is on or it isnt
The Normans Execution-Evaluation cycle : Two Major Phases

Execution phase in which a user performs actions on
the world ( a device or system)

1) Goal 2) Intention 3) Specifying the action sequence 4) Executing the action
Evaluation phase in which the user assesses the state
of the world, to evaluate the results of his actions 5) Perceiving 6) Interpreting 7) Evaluation
The Normans Execution-Evaluation cycle : Reasons Why Some Interfaces Cause Problems to Users
Gulf of Execution
The difference between the users formulation of the action to
reach the goal and the actions allowed by the system If the actions allowed by the system correspond to those intended by the user, the interaction will be effective
Gulf of Evaluation
The distance between the physical presentation of the system
state and the expectation of the user If the user can readily evaluate the presentation in terms of his/her goal, the gulf of evaluation is small
Interface design should aim to reduce the gulfs
The Normans ExecutionEvaluation cycle :Human Error

SLIP
understand system and goal correct formulation of action incorrect action
MISTAKE
may not even have the right goal
How to fix the problem?

slip better interface design mistake better understanding of system
The Normans Execution-Evaluation cycle

Advantages 1) An intuitive and easy means of understanding the
interaction 2) Allows other, more detailed, empirical and analytic work to be placed within a common framework Disadvantages 1) Concentrates only on the users view of interaction 2) Does not deal with the systems communication through the interface
Abowd and Beales Interaction Framework

Extension of Normans model, including the system
communication explicitly Four (4) Components

1) User (U), with task language 2) System (S), with core language 3) Input (I), with input language 4) Output (O), with output language
Abowd and Beales Interaction Framework: Articulation

Articulation Translation
- Users formulation of the desired task to achieve some goals

needs to be translated into the input language (task language input language)
Judged in terms of the coverage from tasks to input
and the relative ease with which the translation can be accomplished - e.g. Direct manipulation interfaces, such as those on Windows
systems, make the articulation of some file handling commands easy
Abowd and Beales Interaction Framework: Performance

Performance Translation
- The responses of the input are translated to stimuli for the system (input language core language) Assessed in terms of whether the translated input language can reach as many states of the system as possible using the system directly - e.g. The remote control unit for a compact disc player does not allow the user to turn the power off on the player unit, hence the off state of the player cannot be reached using the remote controls input language. However, there is a button on the panel of the compact disc player that controls the power. There can be a real effort expended by designer and programmer (cost of implementation)
Abowd and Beales Interaction Framework: Presentation

Presentation Translation
Once a state transition has occurred within the system, the
new state of the system must be communicated to the user by translating the current values of system attributes into stimuli for the output component (core language output language) This translation must preserve the relevant system attributes from the domain in the limited expressiveness of the output devices
e.g. After you finish purchasing a book online, the system should inform you that the
transaction is complete in some way
Abowd and Beales Interaction Framework: Observation

Observation
The response from the output is translated to the stimuli for
the user to observe and assess the results of the interaction relative to the original goal The translation addresses ease and coverage of the final translation
e.g. It is difficult in a command line interface to determine the result of copying and
moving files in a hierarchical file system
Using Abowd & Beales model
Abowd and Beales Interaction Framework: Issues

Issues
This framework is a means to access overall usability of an
interactive system In reality, all the analyses suggested by the framework depend on the current task (set of tasks) in which the user is engaged We judge whether tools are adequate in the context of the particular task(s) we perform
e.g. We use emails when we want to communicate with others asynchronously yet use instant messages or phone calls when we need to communicate with others synchronously

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UNDERSTAND HUMAN INTERACTION

The Terms of Interaction

- a specific action required to meet the goal

The Normans Execution-Evaluation cycle

The Normans Execution-Evaluation cycle: Simple Example

The Normans Execution-Evaluation cycle : Two Major Phases

the world ( a device or system)

Evaluation phase in which the user assesses the state

The Normans ExecutionEvaluation cycle :Human Error

How to fix the problem?

The Normans Execution-Evaluation cycle

Abowd and Beales Interaction Framework

communication explicitly Four (4) Components

Abowd and Beales Interaction Framework: Articulation

- Users formulation of the desired task to achieve some goals

Abowd and Beales Interaction Framework: Performance

Abowd and Beales Interaction Framework: Presentation

transaction is complete in some way

Abowd and Beales Interaction Framework: Observation

moving files in a hierarchical file system

Using Abowd & Beales model

Abowd and Beales Interaction Framework: Issues

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