Introduction to AI & AI Principles (Semester 1) WEEK 5 – Wednesday Introduction to AI & AI Principles (Semester 1) WEEK 5 – Wednesday (2008/09) John Barnden Professor of Artificial Intelligence School of Computer Science University of Birmingham, UK

Reminder Representing the Information in a situation (Planning the Delivery of One Drink, contd)

Reminder Possible Logical Forms, 1(corrected) uD is a door. (D is the door’s name. We might use D-KS, say, as D.) l is-door(D). uD [stated separately to be a door] is open. l is-open(D) uDoor [stated separately to be a door] D is closed. l is-closed(D) ¬is-open(D) l is-closed(D) or ¬is-open(D) uD is an open door l is-door(D)  is-open(D) uMike (M) is in the sitting-room (S). l in(M, S) in(S, M) l in(M, S) or in(S, M) [Caution children! Do it consistently!]

Possible Logical Forms, 2 uD-KS connects the kitchen (K) and sitting-room (S). l door-connects(D-KS, K, S) [but other “argument” orders are usable] uMike is holding B [which is a bottle] [somehow or other] l holds0(Mike, B) uMike’s right hand is free. l is-free(the-right-hand-of(Mike)) uI am holding B in my right hand l holds-in-right-hand(Ego, B) l holds1(Ego, B, the-right-hand-of(Ego))

Possible Logical Forms, 3 uI am holding B in both hands l holds-in-both-hands(Ego, B) l holds2(Ego, B, the-right-hand-of(Ego), the-left-hand-of(Ego)) l holds3(Ego, B) A less good option would be l holds1(Ego, B, the-right-hand-of(Ego))  holds1(Ego, B, the-left-hand-of(Ego)) holds1(Ego, B, the-left-hand-of(Ego)) uI am holding B in one hand l holds1(Ego, B, the-right-hand-of(Ego))  holds1(Ego, B, the-left-hand-of(Ego)) holds1(Ego, B, the-left-hand-of(Ego))

Cautions about Logical Expressions uReminder: the order of “arguments” is arbitrary, holds1 l but you must be consistent for any given “predicate symbol” such as holds1 the-right-hand-of l or for any given “function symbol” such as the-right-hand-of. uA predicate symbol is for constructing assertions (statements that something is the case) about the entities referred top by the arguments in the assertion. uA function symbol is for constructing expressions that refer to entities related to entities referred to by the arguments in the expression. Mike uAn [individual] constant such as Mike or D-KS or B is a basic means for referring to an entity.

Cautions, contd. uThe symbols themselves are arbitrary. zsljkhHGCVnholds1 l E.g., you could use zsljkhHGCVn instead of holds1, JaneMike l or Jane instead of Mike to refer to the person called “Mike”!! uThis is similar to the case of user-chosen names in computer programs. uBut it’s just convenient to invent logical symbols that are similar to appropriate human-language words. uCaution Children! Don’t read too much into symbols that look like words. The AI system doesn’t regard them as words and even if it did would probably not understand them at all, or as richly as you do.

Exercises on Logic Expression 1)holds0(Mike, B)  is-open(D-KH) 2)next-to(Mike,D-KS)   is-open(the-door-of(F)) [remember that F refers to the fridge door] 3)Mike is holding the bottle or I am not holding it. 4)I am next to the fridge and the bottle is in it. 5)I am not holding the bottle in my right hand. 6)The bottle is empty. [Invent a new symbol.] 7)The bottle is full. [Invent a new symbol.] 8)The bottle is neither full nor empty. 9)The bottle is open.