1. Formal Aspects of Computer Science – Week 12 RECAP Lee McCluskey, room 2/07 Email lee@hud.ac.uklee@hud.ac.uk

2. Logic Used in theoretical computer science, language semantics and artificial intelligence Many types of logics – depends on the application Logic languages tend to be very expressive, declarative, equipped with methods of reasoning

3. Prolog A PROGRAMMING LANGUAGE modelled on first order logic No statement sequencing, assignment, iteration, overwrite-able variables in the traditional sense Instead – matching, recursion, 1 data type (the term), simple syntax, backtracking

4. Reasoning with Logic First Order Logic syntactically well formed sentences are called wffs. Reasoning in Logic is about proving that some wff wff1 logically follows from another wff wff2. There are many SOUND laws of inference in Logic which help us do reasoning.

5. Resolution Prolog is in a form of logic called “Clausal Form”. Every Prolog Clause has at least one positive literal. Prolog allows some “extra” and “meta” logical predicates, but its execution is based on the inference rule of Resolution. Resolution is a sound law of inference in FOL. When used in a Resolution Refutation method, using a fair search method, it is also complete. Application: we looked at how logic can be used as a formal specification language.