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CHAPTER 3
the interaction
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EXERCISE 3.1
Choose two of the interface styles (described
in Section 3.5) that you have experience of using.
Use the interaction framework to analyze the interaction
involved in using these interface styles for a database
selection task. Which of the distances is greatest
in each case?
answer
There is no single answer for this exercise,
so we will provide an example of the style of answer
that is suitable and the level of analysis that is
appropriate.
You should be aware that, although the
term distance is used, we have not associated any
real measures to any of the translations in the interaction
framework.
As a result, this analysis can only be
informal and at this point is mainly informed by one's
intuition and experience with various interface styles.
As was stated in Section 3.2.3, assessment
of any interaction with the interaction framework
can only be relative to some task. For this example
we will choose a common database selection task -
selecting records from an online library database.
The two interface styles we will analyze are a natural
language interface and a command line interface.
The task is to select a set of references
from the library database that satisfy some search
criteria. Once the task has been formulated in the
user's task language (for instance, the user wants
to see all of the books written by Alan Dix since
1990), that task must be articulated in the input
language.
A natural language interface style would
allow the user simply to type in the selection query
exactly as they think of it. The articulation distance
is small both because it is easy to articulate (possibly
even easier if a spoken interface is provided rather
than typing), and because the coverage is total (the
user is allowed to articulate anything as a query).
On the other hand, for a command line interface, the
limited vocabulary of the input language makes it
more difficult for the user to articulate a task even
though the limited language provides complete coverage
in terms of possible queries allowed.
The real difficulty for a natural language
interface is how the system translates the input expression
into the actual query that accesses the library records.
This performance translation will be much easier for
the command line interface since it may not even require
any translation of an input expression, that language
having already been constructed with the database
engine in mind.
Therefore, we can see that for a natural language
interface the performance distance is greatest, whereas
for a command line interface it is the articulation
distance that is greatest.
However, the above analysis only really
deals with the execution translations. On the evaluation
side, a natural language interface must try to present
the results of the database query in the form in which
the user phrased the question. This can in general
be a difficult translation for the system as it attempts
to answer questions in the style in which an arbitrary
user has posed them.
Having accomplished that, the observation by the user
should be easy to perform. For a command line interface,
there is no guarantee that the result of the query
will be displayed automatically, and the user may
have to request a display explicitly (and they may
have to express how the display be formatted).
Neglecting that point, presentation by
the system is made easier, as the output language
can be very constrained. Observation is made more
difficult, as the user must translate the output into
the terms of their original task formulation. For
example, having asked for books by Alan Dix published
after 1990, the user may have a difficult time locating
author name and year of publication to determine if
the resulting records match their expectations.
For evaluation, a natural language interface
has a greater presentation distance and a command
line interface a greater observation distance. In
general, therefore, we would expect that a natural
language interface would be easier from the user's
perspective but more difficult from the system builder's
perspective. The opposite should hold for a command
language interface.
There are some issues that we haven't addressed in
this example, such as displaying a large set of records
that satisfy the query, and being able to reuse the
output of one query as the input to another in order
to compound searches easily.
Since the performance translation is
so difficult for a natural language interface style
it is important for a natural language interface to
present the results of the query in such a way that
the user is able to determine if the system understood
the original query in the way the user intended. This
would involve the presentation translation reiterating
both the user's query and the selected records simultaneously.
In our example, since the user was interested in the
author and date of publication, it would help if that
information was prominently presented in the result
set.
We have not considered, either, what
effect experience with the system provides. As users
become more comfortable with the syntax and semantics
of a command language, its perceived difficulty will
decrease. Another problem is that a verbose natural
language output may limit the number of records it
is possible to display from a result set.
The moral of the story is that despite
their intuitive allure, such informal analyses as
suggested by this exercise cannot be the last word
on analysis of an interactive system. Ultimately,
our judgements must be made more precise and concrete.
EXERCISE 3.2
Find out all you can about natural language
interfaces. Are there any successful systems? For
what applications are these most appropriate?
answer
This exercise is intended to encourage
personal research in the form of a brief literature
survey. Appropriate places to begin such a search
would be: general text books on artificial intelligence
(e.g. Janet and Alan's An
Introduction to Artificial Intelligence),
which will include basic information on natural language
processing and famous systems such as SHRDLU; proceedings
from conferences such as the AAAI and specialist journals,
which will have more up to date research papers in
the area; proceedings of HCI conferences such as CHI,
Interact and HCI, which will include natural language
systems particularly geared towards the interface.
Other likely sources are popular journals
such as BYTE and personal computer magazines, which
are likely to review commercial systems. The student's
response to the second part of the question will depend
upon what is unearthed, but it is likely that the
systems that they find out about operate in very constrained
domains and that the natural language used is restricted.
There are as yet no general purpose natural language
interfaces.
EXERCISE 3.3
3.3 What influence does the social environment
in which you work have on your interaction with the
computer? What effect does the organization (commercial
or academic) to which you belong have on the interaction?
answer
The aim of this exercise is to explore
the social and environmental influences that affect
interaction, often without the user being aware of
them. The particular influences will vary from environment
to environment, but we encourage you to consider some
or all of the following.
- work context - Is the work
place shared? Are the machines shared?
- peer pressure - Is there pressure
to compete or impress?
- management pressure - Is there
pressure to achieve? Is the interaction carried
out in the presence of management?
- motivation - What motivates
the interaction? Does this encourage or discourage
experimentation?
- organizational goals
- What is the objective of the organization? (profit?
education? etc.) How does this affect the interaction?
- organizational decision making
- Who determines the systems that you use? Do you
have any choice or influence? Does this influence
the way you interact with the system?
- In each case consider what influence
there may be on the interaction. It may be helpful
to consider other possible environments in order
to identify how the interaction would differ under
these different circumstances. For example, if you
currently share a machine with colleagues, would
your interaction practice change if you were given
a personal machine?
Chapters 13 and 14 also discuss the influence
of groups of workers within an organization on interaction,
and are suggested as further reading material on this
topic.
EXERCISE 3.4
(a) Group the following functions under
appropriate headings, assuming that they are to form
the basis for a menu-driven word-processing system
- the headings you choose will become the menu titles,
with the functions appearing under the appropriate
one. You can choose as many or as few menu headings
as you wish. You may also alter the wordings of the
functions slightly if you wish.
save, save as, new, delete,
open mail, send mail, quit, undo, table, glossary,
preferences, character style, format paragraph, lay
out document, position on page, plain text, bold text,
italic text, underline, open file, close file, open
copy of file, increase point size, decrease point
size, change font, add footnote, cut, copy, paste,
clear, repaginate, add page break, insert graphic,
insert index entry, print, print preview, page setup,
view page, find word, change word, go to, go back,
check spelling, view index, see table of contents,
count words, renumber pages, repeat edit, show alternative
document, help.
(b) If possible, show someone else your
headings, and ask them to group the functions under
your headings. Compare their groupings with yours.
You should find that there are areas of great similarity,
and some differences. Discuss the similarities and
discrepancies.
Why do some functions always seem to
be grouped together?
Why do some groups of functions always get categorised
correctly?
Why are some less easy to place under the 'correct'
heading?
Why is this important?
answer
open-ended investigation
EXERCISE 3.5
3.5 Using your function groupings from
Exercise 3.4, count the number of items in your menus.
(a) What is the average?
What is the disadvantage of putting all the functions
on the screen at once?
What is the problem with using lots of menu headings?
What is the problem of using very few menu headings?
Consider the following: I can group my
functions either into 3 menus, with lots of functions
in each one, or into 8 menus with fewer in each. Which
will be easier to use? Why?
(b) Optional experiment
Design an experiment to test your answers. Perform
the experiment and report on your results.
answer
(a) The answer depends on the answer
to Question 3.4. The problem with putting all functions
on the screen at once is that they will occupy too
much screen space, leaving little room for anything
else. Too many menu headings will make it difficult
for the user to decide under which heading a desired
command resides. Too few menu headings means that
each menu will consist of many menu items, complicating
the visual search task to locate the menu item and
increasing the average length of time it takes to
drag the mouse and select an options. Fitts' Law gives
us a way to understand the impact of length of menu
items and selection times.
We would tend to go for a larger number
of smaller menus, under the assumption that it is
possible to create clear conceptual boundaries between
menu categories. If the eight categories lead to an
easy to understand decomposition of the commands,
then it would be easier to decide which menu to select
and then would be quick to select a menu item among
a small number of options. A small number of menus
might result in an unclear decision on where to place
some menu items.
(b) Open-ended experiment
EXERCISE 3.6
Describe (in words as well as graphically)
the interaction framework introduced in Human-Computer
Interaction. Explain how it can be used to explain
problems in the dialogue between a user and a computer.
answer available for tutors only
EXERCISE 3.7
Describe briefly four different interaction
styles used to accommodate the dialog between user
and computer.
answer available for tutors only
EXERCISE 3.8
The typical computer screen has a WIMP
setup (what does WIMP stand for?) Most common WIMP
arrangements work on the basis of a desktop metaphor
, in which common actions are likened to similar actions
in the real world. For example, moving a file is achieved
by selecting it and dragging it into a relevant folder
or filing cabinet. The advantage of using a metaphor
is that the user can identify with the environment
presented on the screen. Having a metaphor allows
them to predict the outcome of their actions more
easily.
Note that the metaphor can break down,
however. What is the real-world equivalent of formatting
a disk? Is there a direct analogy for the concept
of 'undo'? Think of some more examples yourself.
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