CS789, Spring 2005
Lecture notes, Week 8
We like language for interfaces because it's familiar to so many users. We
can take advantage of an important communication mechanism that users already
know how to use. Language has some properties of which we must be aware
At the current state of the art interfaces can emit language, but they can't
accept it very well.
- Cumulative: What's being said now is context for what comes later.
- Linear: When you and I are in the middle of a conversation we have both
arrived there from the same immediate past, which helps to standardize
- Ambiguous: Resolved by common context maintained by talker and
- Redundant: Handle ambiguity by consistency checking. This is an
important activity that your users are doing all the time!
Spoken versus written language
Spoken and written language are different one from another. With spoken
Written language is different. The reader has
- Some sort of random access:
- Chapters, sections, bookmarks, indices, page numbers
- Titles, paragraph formatting, topic sentences, lists, typographic
Random access is a new property that emerged with the codex, or book
of bound pages. Scholars believe that the codex, which came into common
use a few centuries into the Christian era, changed the nature of
reading, which means `changed the way in which people access the contents
of a particular for of auxiliary memory', and there resulted significant
changes in human culture. `The people of the book' may be more true than
it at first sounds.
- Cues help to move you from one point to another, "as described in
- Semantic cues, like undefined terms.
- Syntactic cues, like the/a, thus, his.
- Stylistic cues, like topic sentences, like naming conventions
(First and last name when first mentioned, last name only
- Typographical cues, like paragraphs, page heads.
Speech cues along this line are limited to `As I just said ...' or
`I'll explain the details in a moment.'
- Communicating emotion requires very skilled writing. Most writers
simply can't do it. Join any newsgroup, read a few blogs, tap into e-mail
miscommunication, listen into a chat room, and you will see many
instances of such failures.
If we are planning to use spoken language extensively in an interface it
is obviously useful to give it some of the attractive properties of written
- Choice points, to which a user can go directly
- Say it again
- These can be encapsulated in CD-player controls
Techniques for putting these into non-specialized interfaces.
- fast forward, with output
- backward, with output
- index points
- speeding up forward and backward buttons
- visual representations of time to give access to control
Language can be described in many different ways. The important one for us
is what it does. In technical terms, this is the performative use of
language, individual parts of which are called speech acts (J. L. Austin).
Our linguistic interaction with interfaces is mainly performative.
- "Hello." -- greets and includes.
- "Pass the meat, please." -- gets some food.
- "The burner is hot." -- keeps your hand off the stove.
- "I promise to pay you Tuesday." -- makes a contract.
- "The cheque's in the mail." -- stop pestering me if you want your
The philosopher H. P. Grice did a lot of work trying to figure out the
properties of speech acts. This turns out to be very hard. Why? Because
there's really a lot of understood content everywhere in language. He
formulated the Cooperative Principle, which says that each
party in a conversation assumes that the conversation itself is a cooperative
activity, and that each party assumes the other parties know the conversation
to be cooperative, and so on. Cooperation is based on the idea that a
dialogue has a purpose. Thus, acts are formulated in language -- words,
sentences, paragraphs -- in the context of mutual agreement with respect to
the purpose of the dialogue. To be sure, purpose evolves during a
conversation. But Grice was able to identify some abstract properties
embodied in all cooperative language acts, regardless of actual purpose.
How are these abstract properties used in practice?
- Listeners continuously test whether or not these maxims are being
- If a failure is detected, meta-processing is attempted to eliminate the
Grice unpacked the Cooperative Principle into four maxims of conversation,
which can be used as design rules when making language for speech acts.
- Maxim of Quantity -- All the necessary information is
given; no unnecessary information is given.
- If something is said there's a reason for it.
- If something is omitted you're already supposed to know it.
- Maxim of Quality -- Information given is true, not
false or misleading.
- If something known to be untrue is said it is assumed to be
intended to mislead, or to indicate ignorance.
- `Known to be untrue' means that a person hearing knows to be untrue
something said by a speaker.
- Language can be made arbitrarily complex in this respect: consider
irony or sarcasm.
- Maxim of Relation -- Information given is relevant to
the goal of the conversation.
- Of the many possible meanings of any language you should select the
one relevant to the shared goal.
- Maxim of Manner -- The communication is clear, brief
and orderly; ambiguity and obscurity is avoided.
- If something seems to be obscure or ambiguous you are probably
Examples of failures:
Here are a few examples of meta-processing
- Maxim of Quantity -- Extra information is given. "On this trip the bus
has a driver."
- Maxim of Quality -- Some information is obviously inconsistent. "Leaves
Kitchener at 8.00am; arrives Guelph at 7.30am."
- Maxim of Relation -- Some of the information seems to be irrelevant.
"There is a good view of the CN tower on this trip."
- Maxim of Manner -- Ambiguity and obscurity is present. "Leaves
Kitchener twenty-three minutes after the mayor starts his speech."
- Maxim of Quantity -- "Tickets are required for this trip." Where do I
find out about trips that don't need tickets?
- Maxim of Quality -- "Express trip, stopping at Guelph." How much more
of the message is not correct? or possiblly, Which part of this message
is not correct?
- Maxim of Relation -- "Beautiful turtles throng the aisles." Where do I
find the table of contents?
- Maxim of Manner -- "Runs on days with `r' in months when oysters are in
season." Is there somebody somewhere who speaks English?
Here are a few other implications of these maxims
There are two other principles that are sometimes tacked on with Grice's
- Maxim of Quantity
- Users ask themselves why anything extra has been included.
- Omissions will be regarded as being significant.
- What is included will be assumed to have been included for a
- What needs to be included depends on what the user already
- Suppose exactly the same piece of language is to be given to two
different users. What must be true?
- Maxim of Quality
- Flag things for which you have incomplete evidence.
- Your user will apply a level of credulity appropriate to the most
- If something usually occurs, say "usually", and give an example of
what else might occur.
- Maxim of Relation
- Let the user know when you are changing topic.
- If the relevance is not obvious, humans will think: "Why is this
being said now?"
- On the other hand, if the relevance is obvious and you explain it
you may be violating the maxim of manner.
- Maxim of Manner
- Use vocabulary and sentence constructions that are appropriate for
the user. You can be too low level as well as too high level.
- Inappropriate manner will make the user say, "I can't do it?" or
possibly "Only morons do it."
- Politeness -- which means that you try to say things that make your
interlocutor feel at ease.
- Postive politeness means including the right things.
- Negative politeness means omitting the wrong things.
- "Meaningless politeness" is often part of a synchronization
- Explicit/implicit expression -- use whichever is easiest on the user
- Sometimes it is necessary to communicate something that will make
your interlocutor lose face; if so make the expression of it
- Users care more about losing face to a computer than they do to
another human, because the computer can't sense the loss of face and
Special Considerations when One Party is a Computer
The above principles apply equally when both parties are human, and also
when one party is a computer. There are, in addition, a few extra principles
that can help to overcome the limitations of a computer interlocutor.
- Assymmetry -- help the user to understand the assymmetry of
comprehension/expression that exists between the user and the computer.
- Let the user know what the interface can and cannot do.
- Provide instructions to the user to inform him or her what the
system can understand.
- Explicitly communicate when commitments are being made.
- When information is acquired from the user provide feedback
indicating what information has been acquired.
- Background knowledge -- because interfaces cannot easily infer the
background knowledge a user has, make the interface work with as wide a
variety of background assumptions as possible.
- Think about possible erroneous inferences and have the interface
prepared to respond to them (politely).
- Alternate dialogues can be used to separate users with different
background knowledge, such as experts and novices.
- Adaptive dialogues allow the interface to customize what is said in
ways that depend on user responses.
- Make certain that the interface has enough task domain knowledge to
respond intelligently to the user's task domain knowledge.
- Repair and clarification -- repair requires 'meta-communication',
communication about the current state of communication.
- Initiate meta-communication if the interface gets into an
- Initiate meta-communication if the user provides inconsistent or
- Human intervention is commonly a fall-back when meta-communication
Grice's Maxims play a role in all dialogue design. Why are they
particularly important for linguistic dialogues? Consider the serial nature