Design Rationale

1
Design Rationale

• Chapter 26
• Brian Barrios
• Alistair Nicol

2
IBIS

• IBIS (Issued-Based Information Systems)
• Technique which was devised in order to capture
  design process itself.
• Considering the pros and cons of alternative
  answers to questions.
• Questions called issues and answers are called
  positions
• The pros and cons are called arguments
• Problems
• Dependencies between issues were not catered for
  that is, no account was taken of whether the
  answer to one questions relied on the answer to
  another.
• Only questions which become issues, that is,
  which are deliberated, are represented on the
  issue map.

3
Design space analysis

• Explorations of the space of alternatives.
• Explore alternatives that fulfill the system's
  specifications.
• Hopefully the designer is forced to explore many
  different options to make the end result better.
• QOC (Questions, Options and Criteria)
• Also uses questions and answers idea.
• Specifically for design instead for general
  questions in IBIS
• Recording Design decisions are time consuming and
  expensive.
• However, though tough to maintain, does result in
  a thorough coverage of important design issues,
  and perhaps the advent of appropriate software
  support tools will support designers using the
  technique.

4
Claims analysis

• A claim relates some aspect of a systems design
  with an important consequence for the user.
• Done by creating scenarios of the systems use
  and analyzing them for claims.

5
Summary.

• Design decisions need to be recorded and
  communicated to many different people.
• Documentation is an inappropriate way to
  communicate design information to users
• Documenting design rationale is a time-consuming
  process
• Design space analysis encourages designers to
  explore more alternatives
• Claims analysis concentrates on refining one
  design.