Design Rationale

1
Design Rationale

• HCI 26

2
Dilemma

• Documentation is usually incomplete,
  inconsistent, poorly organized, written in boring
  prose, confusing and inconsistent
• Many people need to know the reasoning, the
  rationale behind the design to understand it
  better... Why? --gt

3
Why

• Extensions and maintenance is made easier
  (sometimes made possible) by good documentation
• It makes explanations to potential customers
  possible
• It makes training possible, allowing end users to
  build suitable understanding

4
But

• Documentation can be massive
• How would you organize it?
• How would it be accessed?
• By date?
• We will discuss three approaches
• Issue based information systems IBIS
• Design space analysis
• Claims based analysis

5
IBIS

• Questions Issues addressed in the system
• Answers Possible positions taken in answer to
  the issues
• Pros and cons Arguments for each position
• A chart is developed plotting these issues,
  positions and arguments along with relationships
  between them.

6
Procedural Hierarchy of IssuesPHI

• Addresses the issue problem with IBIS IBIS
  only addressed questions that were deliberated
• Hierarchically organized

7
Design Space Analysis

• Supports the exploration of alternative designs
• Results are not solely justification of the
  chosen design but an explanation of why this
  design is better than some alternative

8
Design Space Analysis

• Questions, Options and Criteria
• Questions are issues that must be considered
• Options are the various approaches that would
  address the question
• Criteria argue for (and against) the various
  options

9
Design Space Analysis

• Helps you think about the design space
• Shows positive and negative relationships between
  criteria and options
• BUT it doesnt itself point out the best option

10
Claims Analysis

• Examines psychological claims (made by the
  designer) about the use of the system, the users
  of the system or the user environment where
• A claim relates some important aspect of the
  system to an important consequence for the user

11
Claims Analysis

• First build scenarios of use for the system
• Then examine them for claims
• This approach concentrates on analyzing and
  refining one design (contrast with Design Space
  Analysis)

12
The End!