Q! Discuss the ways in which a full-page word processor is or is not a direct manipulation interface
for editing a document using Shneiderman’s criteria. What features of a modern word processor
break the metaphor of composition with pen (or typewriter) and paper?
Answer We will answer the first point by evaluating the word processor relative to the criteria
for direct manipulation given by Shneiderman.
Visibility of the objects of interest
The most important objects of interest in a word processor are the words themselves.
Indeed, the visibility of the text on a continual basis was one of the major usability
advances in moving from line-oriented to display-oriented editors. Depending on the
user’s application, there may be other objects of interest in word processing that may
or may not be visible. For example, are the margins for the text on screen similar to
the ones which would eventually be printed? Is the spacing within a line and the line
breaks similar? Are the different fonts and formatting characteristics of the text visible
(without altering the spacing)? Expressed in this way, we can see the visibility criterion
for direct manipulation as very similar to the criteria for a WYSIWYG interface.
Incremental action at the interface with rapid feedback on all actions
We expect from a word processor that characters appear in the text as we type them
in at the keyboard, with little delay. If we are inserting text on a page, we might also
expect that the format of the page adjust immediately to accommodate the new changes.
Various word processors do this reformatting immediately, whereas with others
changes in page breaks may take some time to be reflected. One of the other important
actions which requires incremental and rapid feedback is movement of the window
using the scroll button. If there is a significant delay between the input command to
move the window down and the actual movement of the window on screen, it is quite
possible that the user will ‘overshoot’ the target when using the scrollbar button.
Reversibility of all actions, so that users are encouraged to explore without
severe penalties
Single-step undo commands in most word processors allow the user to recover from
the last action performed. One problem with this is that the user must recognize the
error before doing any other action. More sophisticated undo facilities allow the user
to retrace back more than one command at a time. The kind of exploration this reversibility
provides in a word processor is best evidenced with the ease of experimentation
that is now available for formatting changes in a document (font types and sizes and
margin changes). One problem with the ease of exploration is that emphasis may move
to the look of a document rather than what the text actually says (style over content).
174 Chapter 4 n Paradigms
Syntactic correctness of all actions, so that every user action is
a legal operation
WYSIWYG word processors usually provide menus and buttons which the user uses
to articulate many commands. These interaction mechanisms serve to constrain the
input language to allow only legal input from the user. Document markup systems,
such as HTML and LaTeX, force the user to insert textual commands (which may be
erroneously entered by the user) to achieve desired formatting effects.
Replacement of complex command languages with actions to manipulate
directly the visible objects
The case for word processors is similar to that described above for syntactic correctness.
In addition, operations on portions of text are achieved many times by allowing
the user to highlight the text directly with a mouse (or arrow keys). Subsequent action
on that text, such as moving it or copying it to somewhere else, can then be achieved
more directly by allowing the user to ‘drag’ the selected text via the mouse to its new
location.
To answer the second question concerning the drawback of the pen (or typewriter)
metaphor for word processing, we refer to the discussion on metaphors in Section
4.2.6. The example there compares the functionality of the space key in typewriting versus
word processing. For a typewriter, the space key is passive; it merely moves the
insertion point one space to the right. In a word processor, the space key is active,
as it inserts a character (the space character) into the document. The functionality of
the typewriter space key is produced by the movement keys for the word processor
(typically an arrow key pointing right to move forward within one line). In fact, much of
the functionality that we have come to expect of a word processor is radically different
from that expected of a typewriter, so much so that the typewriter as a metaphor for
word processing is not all that instructive.
for editing a document using Shneiderman’s criteria. What features of a modern word processor
break the metaphor of composition with pen (or typewriter) and paper?
Answer We will answer the first point by evaluating the word processor relative to the criteria
for direct manipulation given by Shneiderman.
Visibility of the objects of interest
The most important objects of interest in a word processor are the words themselves.
Indeed, the visibility of the text on a continual basis was one of the major usability
advances in moving from line-oriented to display-oriented editors. Depending on the
user’s application, there may be other objects of interest in word processing that may
or may not be visible. For example, are the margins for the text on screen similar to
the ones which would eventually be printed? Is the spacing within a line and the line
breaks similar? Are the different fonts and formatting characteristics of the text visible
(without altering the spacing)? Expressed in this way, we can see the visibility criterion
for direct manipulation as very similar to the criteria for a WYSIWYG interface.
Incremental action at the interface with rapid feedback on all actions
We expect from a word processor that characters appear in the text as we type them
in at the keyboard, with little delay. If we are inserting text on a page, we might also
expect that the format of the page adjust immediately to accommodate the new changes.
Various word processors do this reformatting immediately, whereas with others
changes in page breaks may take some time to be reflected. One of the other important
actions which requires incremental and rapid feedback is movement of the window
using the scroll button. If there is a significant delay between the input command to
move the window down and the actual movement of the window on screen, it is quite
possible that the user will ‘overshoot’ the target when using the scrollbar button.
Reversibility of all actions, so that users are encouraged to explore without
severe penalties
Single-step undo commands in most word processors allow the user to recover from
the last action performed. One problem with this is that the user must recognize the
error before doing any other action. More sophisticated undo facilities allow the user
to retrace back more than one command at a time. The kind of exploration this reversibility
provides in a word processor is best evidenced with the ease of experimentation
that is now available for formatting changes in a document (font types and sizes and
margin changes). One problem with the ease of exploration is that emphasis may move
to the look of a document rather than what the text actually says (style over content).
174 Chapter 4 n Paradigms
Syntactic correctness of all actions, so that every user action is
a legal operation
WYSIWYG word processors usually provide menus and buttons which the user uses
to articulate many commands. These interaction mechanisms serve to constrain the
input language to allow only legal input from the user. Document markup systems,
such as HTML and LaTeX, force the user to insert textual commands (which may be
erroneously entered by the user) to achieve desired formatting effects.
Replacement of complex command languages with actions to manipulate
directly the visible objects
The case for word processors is similar to that described above for syntactic correctness.
In addition, operations on portions of text are achieved many times by allowing
the user to highlight the text directly with a mouse (or arrow keys). Subsequent action
on that text, such as moving it or copying it to somewhere else, can then be achieved
more directly by allowing the user to ‘drag’ the selected text via the mouse to its new
location.
To answer the second question concerning the drawback of the pen (or typewriter)
metaphor for word processing, we refer to the discussion on metaphors in Section
4.2.6. The example there compares the functionality of the space key in typewriting versus
word processing. For a typewriter, the space key is passive; it merely moves the
insertion point one space to the right. In a word processor, the space key is active,
as it inserts a character (the space character) into the document. The functionality of
the typewriter space key is produced by the movement keys for the word processor
(typically an arrow key pointing right to move forward within one line). In fact, much of
the functionality that we have come to expect of a word processor is radically different
from that expected of a typewriter, so much so that the typewriter as a metaphor for
word processing is not all that instructive.
Q3 Solution
Q2 Solution
Some diagrammatic notations may be clear enough to be used in user documentation as well as in
design. Figure 16.15 shows a state transition diagram for the major modes of a digital watch, taken from
the instruction booklet. The booklet goes on to use some similar diagrams and some tabular descriptions
of each of the modes (using the other two buttons).
The watch has only three buttons, and only one of these, button A, is used to move between modes.
As the diagram is being used in documentation, the states are denoted by representations of the watch
in the appropriate mode. This is a useful approach for any stage in the design process, and is similar to
the use of screen images in the flow diagram in Figure 16.13.
There are four modes, and pressing the button A moves between them. The most common modes are
the time display and stop watch. So the dialog is designed to make it easy to switch between these
modes and difficult to slip accidentally into the time- or alarm-setting modes. To achieve this aim, pressing
‘A’ usually toggles between the two main modes. However, the watch’s owner will want to set the
time eventually, and the designer does not want another button to be used (buttons cost money and
the watch only costs £2). Therefore, the setting modes are achieved by holding the button down for
two seconds or more. So, a quick press does one thing, whereas a long one does something else. The
semi-formal nature of a state transition diagram makes this real-time behavior easy to denote. It is
merely added as textual commentary.
But this documentation diagram does not have all the information one would require for design purposes.
If you are in the time-setting mode and press ‘A’, what happens? Do you go to the time display
or to the stop watch? Also, when going from time display to alarm setting, what do you see during the
two seconds you hold down button A?
design. Figure 16.15 shows a state transition diagram for the major modes of a digital watch, taken from
the instruction booklet. The booklet goes on to use some similar diagrams and some tabular descriptions
of each of the modes (using the other two buttons).
The watch has only three buttons, and only one of these, button A, is used to move between modes.
As the diagram is being used in documentation, the states are denoted by representations of the watch
in the appropriate mode. This is a useful approach for any stage in the design process, and is similar to
the use of screen images in the flow diagram in Figure 16.13.
There are four modes, and pressing the button A moves between them. The most common modes are
the time display and stop watch. So the dialog is designed to make it easy to switch between these
modes and difficult to slip accidentally into the time- or alarm-setting modes. To achieve this aim, pressing
‘A’ usually toggles between the two main modes. However, the watch’s owner will want to set the
time eventually, and the designer does not want another button to be used (buttons cost money and
the watch only costs £2). Therefore, the setting modes are achieved by holding the button down for
two seconds or more. So, a quick press does one thing, whereas a long one does something else. The
semi-formal nature of a state transition diagram makes this real-time behavior easy to denote. It is
merely added as textual commentary.
But this documentation diagram does not have all the information one would require for design purposes.
If you are in the time-setting mode and press ‘A’, what happens? Do you go to the time display
or to the stop watch? Also, when going from time display to alarm setting, what do you see during the
two seconds you hold down button A?
