CS349 - Implementing User Interfaces - Spring 2010

Public Service Annoucements

1. Mid-term: 17 June, 2010, MC4059.

Lecture 17 - Users II

Exploiting What Users Know

Two user interface design objectives

1. Consistency.

Exploit the skills users already have with computers.

2. Congruence.

Much meaning is created by analogy, often called metaphor in the user interface community.

• `Metaphor' refers to the model that users create to learn the behaviour of an interface.

What English scholars call `not mixing your metaphors' lies very close to what is meant by congruence.

• Examples of mixed metaphors.
  • I have tried to build the course on a solid foundation, and to teach without allowing its life-blood to be sucked away.
  • When implementing user interfaces we should not bury our heads in the sand and ride rough-shod over the needs of our users.
  • When doing assignments you should not throw in the sponge when the bugs are in retreat.
• What does `not mixing your metaphors' mean?
• The metaphor is the mental model that users have, helping them to predict how do understand and do things
  • For example, the interface is `just like' a desktop. I should expect to find
    1. pieces of paper, documents,
    2. things that collect together pieces of paper, file folders, (Notice how the Unix usage of `file' is incongruent with the normal office usage of `file', as in `filing cabinet', and how desktop systems try to reconcile these two usages by using `folder' for the thing that Unix calls a `directory' and ordinary office usage calls a `file'.)
    3. a waste basket, which is usually on the floor, so it should be near the bottom of the display.

       (Or should it? Surely the display, which is vertical, is supposed to mimic the horizontal surface of the desktop. If so, then what logic suggests that the waste basket should be at the bottom of the display. Obviously, the display simultaneously has its real properties, like vertical, and its metaphorical properties, like horizontal.

       Sometimes real and metaphorical properties conflict, as in the Renforth Road sign; more often they coincide. Here's an unexpected and fortunate coincidence. The transformation of the desktop from vertical to horizontal loccurs by rotating the top away from the user. So the bottom of the display corresponds to the near portion of the desktop, where users' attention tends to focus when working at a desk. Fortunately, users tend to focus their attention on the bottom of the display. Exercise for the reader. Knowing this how do we apportion interface stuff between the top and bottom of the display?)

  • Exercise for the reader. Think about the metaphor intended by the designer, and the metaphor you use for commonly used interfaces.
• Because the `mental model' is such a powerful way of learning and remembering it is very common that tutorials, documentation, help systems and interface presentation all refer to a single metaphor chosen by the designer, and which the user is expected to learn.

Congruence exists at high and low levels.

• High level
  • Desktop metaphor - spatial versus temporal access to things arranged different ways on the desktop.
  • Desktop metaphor - emptying wastebasket
• Low level
  • if you `enter' an application, you should `exit' from it;
  • if you `start' an application you should `end' it;
  • if you `open' an application, you should `close' it

At the basis of these objectives

1. What do users know?
   • They will augment knowledge they have already when they are learning an interface.
2. How do users learn beyond what they know?
   • Learning should be, as much as possible, incremental

Learning

Ways of changing knowledge = `learning'

Techniques of learning

1. Trial-and-error: putting on a nut, riding a bicycle
2. Practice = rehearsel: using a hammer, playing the piano.
3. How-to-do it descriptions: cookbook recipes
4. Modification of examples: making html pages
5. Solving a problem: and remembering that we did it.
   • Analogy is a common way of solving problems, and of remembering the solution.

All these take time.

• 1, 2: do it over and over again. If you can do it slowly, do it as slowly as you need to , then speed it up with practice
• 3, 4: break what you want to learn down into parts that you can do
• 5: assembling facts, mental rehearsel of plans
• How much time?
• What incentives are we (users) normally given to spend the time?

Principles

Users are assumed not to be using interfaces just for the fun of using interfaces. They are assumed to be using them because they have some other goal, writing lecture notes for CS349, creating a memo that will get a raise from their boss, etc. They want to use as little mental effort as possible managing the interface, so that they can concentrate as much effort as possible on their real goal. This leads to two important principles.

1. The less learning users have to do the better.
2. The less thinking user have to do the better.

To arrange this take advantage of `learning transfer':

1. within an interface
2. between one interface and another
3. between an interface and life

The main tool we have for arranging these properties is look-and-feel

• the important point: these communicate with the lower levels of the user's brain
  • They are only poorly communicated by words

Look-and-Fell

The obvious goal is to have the user select the correct response as effortlessly as possible. This means that an interface should communicate its metaphor as implicitly as possible; but the communication mode must be very reliable. Misunderstanding the metaphor, and at a low level of processing where processing is effectively unlimited (ie.e, effortless) can be error-prone. Fortunately, the lowest levels of communication are the most error-free; unfortunately, they are the hardest to use effectively. They utilize users' abilities to synthesize a large number of low level cues into the holistic perception of a particular environment.

Users have strong abilities to associate collections of perceptual and motor responses to particular environments. When they do so they associate a collection of specific low-level responses with a particular environment/interface. For example, when you are driving in a car, even in the passenger seat, a traffic light changing from green to yellow automatically activates fast-twitch muscles in the thigh and calf of the right leg. The same does not occur when you are walking, where you experience the same visual stimulation in a different environment.

`The collection of features we describe as an interface's look-and-feel should define it aa a specific cognitive environment.' At least this would be true in a world where each interface is completely separate from every other interface and from every non-computer environment inhabited by users. But the reality is, that environments are composed of many parts and that subcollections of parts are specifically associated with subcollections of responses. Thus, environments interpenetrate each other on many levels.

Doing the best thing consistently and comprehensively is not easily learned, and is usually the result of a lifetime of sensitivity to all the different cognitive environments we inhabit. The next few sections are only a very brief introduction to a topic that is both important and subtle.

Look

How do we go about decorating a house?

• to create different activity levels and moods
• to make salient (cognitively available) things that are used
  • improve decisions about what to use
• to make ourselves - and others - comfortable with the activities that ought to go on in these spaces
• to make ourselves - and others - feel good

Exercise for the reader. Turn all these - and more - aspects of the house-decorating metaphor into the corresponding features of the user interface.

Feel

What do we want in the feel of something?

• predictability, so we can learn muscle activitation sequences
  • timed to 1 millisecond precision
  • predictability is essential for transferring stuff to lower levels of control
• low level feedback (mostly muscle stretch receptor feedback)
  • probably the most important level of monitoring and control
• fit with user abilities and capabilities
  • It's obvious, but easy to overlook, that users have windows in their sensory and motor capabilities, and they need the demands and information content of a task to be within these windows of capability.

Note. Most look is programmable, but the same code is not guaranteed to have the same look on different platforms. Even more so the programmable portion of feel is not guaranteed to be the same on different platforms. (The Macintosh interface, which cares more about this than any other, handles this problem by running only on one particular set of - often over-priced - hardware. The obvious generalization for this practice would be standards for hardware. Research topic. Develop ways of having reproducible feel in instances of a user interface running on different hardware configurations.)

How to create a uniform look-and-feel

1. UI architect
   • trusted by implementers
   • has absolute power
   • Apple did this by making its UI people into industry super-stars
     • (Part of the result was generally excrable implementation.)
2. User interface toolkit
   • appeal to lower nature of implementers
3. Widely understood metaphor
   • appeal to higher nature of implementers

Note. It is possible to appeal simultaneously to the higher and lower nature of implementers.

User Interface Toolkits - A history

What we're usually talking about when discussing `look-and-feel'.

Here's the problem.

• You are (Apple) introducing a new computer/OS.
• People will buy it only if they have applications they can use easily.
• Having decided from a business point of view that there's no money in applications, you want lots of `other people' to create lots of applications.
• You want all the applications to `go with' your new OS concept.

How do you arrange for this?

1. Model for inter-application cut-and-paste. (Clipboard, scrapbook).
2. Common look-and-feel, which means using a common set of rules and operations.
   • Model applications
   • User interface guidelines
   • User interface university
   • Movie star interface designers
     • which, of course, created a whole generation of wanna-be interface designers
   • User interface toolkit

In Apple's case the toolkit, at first, was just added ad hoc to the graphics model.

• but with very large amounts of user testing
  • which is hard to distinguish from what?
  • Hint. If you make it (them) fit user preferences what will they look like taken together.

Note. Real benefits came from a restricted `palette'.

X, on the other hand, was done by a bunch of professors and grad students.

• funded by Digital Equipment Corporation - subsequently taken over by Compaq.

A new thesis topic, or more likely, grant application -

• encapsulate bundles of Xlib atoms into molecules of higher level functionality
  • buttons
  • menus
  • dialogue boxes
  • text fields
• use callbacks to produce a new programming style
• the atoms of functionality were called `widgets'.

Basic motive not commercial, so little attention to look-and-feel, which are for suits (marketers).

• every look in creation - almost all abominable.
• feel didn't yet exist.

NeWS went for a Spartan look,

• the look that is most likely to be platform-independent

and much better feel,

• and lost the battle for `mind-share'.
• Hmmm.

Widget Sets

Essential properties of widget sets.

• Complete. An application designer should never need anything that isn't in the set.
• Consistent. They should share both look and feel.
• Customizable. Enough but not too much.

Return to:

• CS349 - Spring 2010 - Lecture schedule
• CS349 - Spring 2010
• CS349 page
• Bill Cowan's home page.