Imran Hussain University of Management and Technology (UMT)

Virtual University - Human Computer Interaction1 © Imran Hussain | UMT

Imran Hussain

University of Management and Technology (UMT)

Lecture 36

Behavior & Form – Part IV

Virtual University

Human-Computer Interaction


In Last Lecture …

• Evaluation– Conceptual framework for developing an interactive product

– How we can use this framework to identify certain usability problems

– Tactical vs. strategic usability


Usability can be tactical as well as strategic


In Today’s Lecture …

• Undo functionality

• Files and Save functionality


Understanding Undo


Users and Undo

• Reverses previous action


User Mental Models of Mistakes

• Humans make mistakes

• Programmers should not think of human mistakes as errors

• Programmers follow implementation model

• Human being do not like to be told that they have make an error so the software should not contradict users


Undo Enables Exploration

• Users are like explorers using a tool

• They like experiment to see what they can achieve with computer

• Undo reassures user if they are in trouble then this function helps them to reverse any action


Designing an Undo Facility

• Undo not directly related to goal of user

• Users have different models of undo– Novice: help

– Intermediate: deleted data

– Expert: stack of procedures that can be undone

• Undo should be designed to support exploration and not for reversing errors

• Undo should be global-wide function


Types of Undo

• Incremental and Procedural Actions

• Blind and Explanatory Undo

• Single and Multiple Undo

• Redo


Incremental and Procedural Actions

• Procedural component• What the user did?

• Data component• What information was affected?

• Incremental actions there is both procedural component and data component

• Procedural actions do not have data component– These operations act on data but do not add or delete the data


Blind and Explanatory Undo

• Blind Undo– There is no indication what the operation is

• Explanatory Undo– There is some textual and visual information of the particular operation


Single Undo

• Most common form of undo• It reverses the effects of the most recent user’s action


Other Models for Undo-like Behavior

• Comparison

• Category-specific undo

• Deleted data buffers

• Milestoning and reversion

• Freezing


Other Models for Undo-like Behavior

• Comparison

• Category-specific undo• Deleted data buffers

– Saves the user having to remember exact undo operations and their sequence

• Milestoning and reversion– For significant changes make a milestone copy, use revert option to

access it

• Freezing– Lock the document so certain aspects cannot be changed


What’s wrong with saving changes to files …


Saving Changes to Files

• Programs and data files exist in 2 places at the same time

• Data and program managed by file system– Explorer (Windows)

– Finder (Mac)

• The file system and the disk storage facility it manages is the primary cause of disaffection in computer users


Let’s consider the ‘save as’ dialog box …


what’s the point in having a redundant dialog box that users always click yes?

…


what’s the point in a function that will confuse new users and they might click ‘no’?


.. confuses possibility with probability (poor assumption)


… why would someone close the document if they didn’t want the changes


… why does it ask for saving changes when you are done and not when making them?


saving changes -------- closing doc(compare with writing in a notebook)

when user closes doc, this is the time the differences between the memory and disk need to be reconciled

no obvious connection, e.g.- erasing notes when closing book- discarding changes when we leave room


Reason?

implementation model is rendered as interface for users


Problems with implementation model …


What happens when I try to rename a file …


Q: What’s the function of the ‘save as’ window?Ans: placing and naming a file


I close the ‘save as’ dialog box, go to ‘explorer’, and try renaming again …


Another example:

What happens when I then open the document make some changes that don’t make difference to the contents of the file …


So why do we have these problems …


The Computer’s File System

• Data and program managed by file system– Explorer (Windows)

– Finder (Mac)

• File system is an internal facility and shouldn’t affect the user

• Software applications (you) treat file system (a car) just like the OS (a mechanic) does


Let’s say you want to create a copy for archive …

[no explicit function for creating copy

have to use ‘save as’]


… have to close ‘hci2.doc’, go to explorer, and then reopen original file


And now a perfectly reasonable scenario:

have made changes to doc (without saving) and now want to create a copy and keep on working …


… invoke ‘save as’ ..

… new file ‘hci2.doc’ contains changes, not ‘hci.doc’


I work on new file and delete those recent changes ..


… now I reopen the original file …


… changes lost forever!


Implementation Model vs. Mental Model

• Users view electronic documents just like printed documents

Imran Hussain University of Management and Technology (UMT)

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