Conceptual Models

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Conceptual Models
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Conceptual model

• A conceptual model is
• a high-level description of how a system is
  organized and operates. (Johnson and Henderson,
  2002, p. 26)
• Need to first think about how the system will
  appear to users (i.e. how they will understand
  it)

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From David Liddle

• The most important thing to design is the
  conceptual model. Everything else should be
  subordinated to making that model clear, obvious
  and substantial. That s almost the opposite of
  how most software is designed
• (Liddle, 1996, p.17)

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What is a conceptual model?

• It is NOT a description of the user interface
• It is an abstraction (structure) that outline
  what people can do with a product and what
  concepts are needed to understand how to interact
  with it.

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Why a conceptual model is needed?

• Why not start with the nuts and bolts of design?
• Architects and interior designers would not think
  about which colour curtains to have before
  deciding where the windows will be placed in a
  new building
• Enables designers to straighten out their
  thinking before they start laying out their
  widgets (p. 28)
• Provides a working strategy and a framework of
  general concepts and their interrelations

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Conceptual models help the design team

• Orient themselves towards asking questions about
  how the conceptual model will be understood by
  users
• Not to become narrowly focused early on

• Establish a set of common terms they all
  understand and agree upon
• Reduce the chance of misunderstandings and
  confusion arising later on

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Main components of a conceptual model

• Major metaphors and analogies that are used to
  convey how to understand what a product is for
  and how to use it for an activity.
• Concepts that users are exposed to through the
  product
• The relationships between the concepts
• e.g., one object contains another
• The mappings between the concepts and the user
  experience the product is designed to support

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A classic conceptual model the spreadsheet

• Analogous to ledger sheet
• Interactive and computational
• Easy to understand
• Greatly extending what accountants and others
  could do

www.bricklin.com/history/refcards.htm
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Why was it so good?

• It was simple, clear, and obvious to the users
  how to use the application and what it could do
• it is just a tool to allow others to work out
  their ideas and reduce the tedium of repeating
  the same calculations.
• capitalized on users familiarity with ledger
  sheets
• Got the computer to perform a range of different
  calculations and recalculations in response to
  user input

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Another classic

• 8010 Star office system targeted at workers not
  interested in computing per se
• Spent several person-years at beginning working
  out the conceptual model
• Simplified the electronic world, making it seem
  more familiar, less alien, and easier to learn

Johnson et al (1989)
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The Star interface
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Activity

• Compare the conceptual models for Visicalc and
  the star interface
• 1.What similarities do they share in their use
  of analogy and core concepts?
• 2. How do they differ?

Text p 53
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Summary points

• A conceptual model is a high-level description of
  a product
• what users can do with it and the concepts they
  need to understand how to interact with it
• Decisions about conceptual design should be made
  before commencing any physical design
• Interface metaphors are commonly used as part of
  a conceptual model