人工智能教学资料 1ai Logic Artificial Intelligence.pdfVIP

Artificial Intelligence Logic Yanghui Rao Assistant Prof., Ph.D School of Mobile Information Engineering, Sun Yat-sen University Artificial Intelligence: Logic Grading Scheme ? Final Exam (40%) ? Project (35%) ? Group project ? To be evaluated in technical innovation, thoroughness of the work, clarity of presentation, etc. ? Algorithm design ? Report based on existing tools ? Survey on a topic in AI ? … ? Others (25%) Artificial Intelligence: Logic Logic ? Logic: the knowledge is mainly input/transferred by experts ? Machine Learning: the knowledge is mainly learnt by computers ? Logic is a great knowledge representation language for many AI problems ? Propositional logic (PL) is the simple foundation and fine for some AI problems ? First order logic (FOL) is much more expressive and more commonly used in AI ? There are many variations: horn logic, higher order logic, three-valued logic, probabilistic logics, etc. Artificial Intelligence: Logic Propositional Logic (PL) ? Logical constants: true, false ? Propositional symbols: P, Q,... (atomic sentences) ? Wrapping parentheses: ( … ) ? Sentences are combined by connectives: ? and [conjunction] ? or [disjunction] ? implies [implication / conditional] ? is equivalent [equivalence] ? not [negation] ? P ? Q, ?P ? Q, ?P ? Q, ((P) ? Q), etc. Artificial Intelligence: Logic PL ? Simple language for showing key ideas and definitions ? User defines set of propositional symbols, like P and Q ? User defines semantics of each propositional symbol: ? P means “It is hot”, Q means “It is humid”, etc. ? A sentence (well formed formula) is defined as follows: ? A symbol is a sentence ? If S is a sentence, then ?S is a sentence ? If S is a sentence, then (S) is a sentence ? If S and T are sentences, then (S ? T), (S ? T), (S ? T), and (S ? T) are sentences ? If expressions are parenthesized, the term in the parentheses is evaluated first. Otherwise, the priorities are: ?, ?, ?, ?, ? Artificial Intelligence: Logic Examples of PL Sent