When to Use Forward and Backward Chaining

• The problem being solved tells you which is best!
• Forward is best if
  • There is no obvious goal to set
  • All of the data is already there
  • There are many possible goals and a small number of patterns
  • tends to be better for small systems
• Backward is best if
  • Data is expensive
  • Explanation is important
  • There is a lot of possible data and a lot of goals
  • It tends to be better for medium sized systems
• In class box-world exercise:
• You have 2 boxes name A and B. A is on-top of B.
• What does WM look like?
• What do rules look like?
• The goal is to have B on-top of A.
• How does the goal stack change, and when are rules applied?
• State space and fan out and fan in (section 2.1)