Queries

• If you have a knowledge base of facts, you can usually derive more facts.
• The user or system can look for particular facts.
• So is tall(John)?
• Or ∃ x (student3170(x) -> first(x)) did anyone in 3170 get a first?
• The problem is this can be very computationally expensive.
• Of course this is often what you want from logic.
• A lot of folks at Middlesex are working on proving things like this code will not fail if there is no more dynamic memory.
• They use some form of logic to prove that a system is correct.
• Modus Ponens: If you know A->B and A, then you can derive B.
• Modus Tollens: If you know A->B and -B, then you know -A.