Transcript Knowledge and Mental Models

Design Rationale
Chapter 26
Brian Barrios
Alistair Nicol
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.
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.
Claims analysis
• A claim relates some aspect of a system’s design with an important
consequence for the user.
• Done by creating scenarios of the system’s use and analyzing them
for claims.
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.