CS 160: Lecture 8
Administrivia
- Contextual inquiry/ task analysis due today (in class)
Knowledge representation
- Analogical representations
- Propositional representations
- Distributed representations
Connectionist view
- Connectionist view: Knowledge is arranged in networks with inhibition/activation
- Sort-of example: tools from thebrain.com
Semantic networks
- Associations between items defined by relations:
Schema
- Generalized scripts for everyday actions:
- Eat at a restaurant
- Enter
- Walk in
- Look for table
- Decide where to sit
- Go to table
- Sit Down
- Order...
- Eat...
- Leave...
Mental Models
- “The models people have of themselves, others, the environment, and the things with which they interact. People form mental models through experience, training and instruction” - D. Norman
- Something like activated schema.
- Not just an image: MMs allow us to visualize what would happen if we do something
Some Piaget
- Piaget notes that there are 3 distinct stages of development.
- Stage 1 is sensori-motor or skill learning.
- But then there are two distinct “abstract” stages:
- e.g. children learn to navigate by concrete transformations before they learn to use maps.
Structural vs. Functional Models
- A structural model explains what the system does independent of use (it’s a system-centered model).
- A functional model explains what the system does to assist a user’s task (it’s a user-centered model)
Functional Models
- Should sound something like task analysis. In fact functional models have been called “task-action mapping models”.
- Develop from knowledge of using similar artifacts, not from how the artifact works.
- Generally strive to be much simpler than structural models. But...
Accountable Systems
- There is a problem if functional and structural models are too far out of step: exceptions to the functional model confuse the user, and may disrupt the task.
- Some researchers are therefore developing “accountable” systems that externalize a user-friendly structural model.
Metaphor
- Since functional models draw on past experience and not everyone has computer experience, its useful to draw on the real world.
- Hence the “desktop metaphor”:
- Directories are like folders
- Files are like sheets of paper
- Windows are like ?:
- Menus are like menus
- Deleting is like putting in the trash
- Running an application program is like opening the doc.
- Copy to buffer and restore is like cut-and-paste...
Metaphor
- Metaphor is basic to human language for a similar reason: it allows us to talk about knew or abstract things by drawing on familiar experience:
- Time is like a line we move on
- We can go forward and look back
- We can push a meeting back
- Love is like a journey (also like a fall)
- Even abstract fields, like math or quantum mechanics, are rich with metaphors
Metaphor: Strenghs
- Gives a way for people to understand a new concept quickly given what they know.
- Helps to provide good choices for terminology.
- Provides guidance in machine understanding of natural language.
Metaphor: Difficulties
- The metaphor may create expectations that are false along with the true ones:
- Can I shred this file instead of putting in the trash can?
- Our understanding is “functional” rather than “structural”. That means understanding is relative to how we do things.
- For instance “work” has many meanings:
- Something we enjoy, or dislike
- Something that is primarily physical, vs. intellectual
- Something that leads to a goal, vs. something we just do
Development & Vygotsky
- Beyond a fairly early age, our understanding of concepts is personal and our conceptual models diversify (Piaget)
- Knowledge is usually deeply layered, so it understanding depends on our personal history
- Our “environment” is a social one as well as a physical one:
- Knowledge work is about organization, communication, persuasion, motivation
- “Culture” is a set of norms guiding our behavior
- The artifacts (programs, documents) in our world also have history, and so there are even layers of meaning outside of people’s heads.
Reverse metaphor
- Computer notions are permeating everyday life:
- I had a head crash thinking about it
- This report is still buggy
- We need to stop and reboot
-
- It will be increasingly easy to draw metaphors from popular computer systems
Desktop metaphor
- Most of the Star’s metaphors are visual ones:
A Virtual Desktop
- The metaphor can help decide on what functionality is useful to the user.
- E.g. the sales rep who worked from a car, and said the car was like “a desk” rather than “an office”.
- Note that people experience the desktop metaphor by using it, rather than being told about it. Therefore they have a better chance to develop a functional model, and to act “by perceiving” rather than “by recognizing”.
Composite Metaphors
- People are usually happy stepping out of the metaphor:
- Scroll bars
- Resizing
- Iconifying
-
- Users can use multiple metaphors at once, or other models based on familiar practice
- Over time, the original metaphor becomes redundant and the user has a new concept and set of skills.
Conceptual Models
- Because of the difficulties with metaphors, the goal of interface design is typically to come up with a clean “conceptual model”.
- A conceptual model is the user’s model of what happens. A good one acknowledges human ability:
- Simplicity, how much to learn, how easy to apply?
- Limited short-term memory
- Expensive long-term memory
- Stimulus-action fusion
Summary
- Knowledge models provide guidance to how to plan an interface (and the user’s model of it)
- Functional models are usually the goal, but its useful to expose some system behavior to help in exceptional situations
- Metaphors often provide a quick way to bootstrap use of an interface
- Conceptual models are more general, and can use knowledge of
- Other systems
- Social/cultural norms