Transcript Tuesday parts A and B: Lecture and Exercises

Introduction to AI
&
AI Principles (Semester 1)
WEEK 4 – Tuesday parts A and B
(2008/09)
John Barnden
Professor of Artificial Intelligence
School of Computer Science
University of Birmingham, UK
The “Big Picture” for the Module
We’ve done some scene setting, getting an idea of what
AI is, getting to know a little of how to think about AI
situations, and seeing a few broad issues in AI (contextsensitivity, reasoning, uncertainty, default assumptions,
diversity of information, difficulties with language,…)
We’ve established three Case Studies (Hot Drinks party,
Shopping Trip, Crime Prevention) as a framework for
getting down to detail.
The rest of the module will largely be the detail …
involving “serious exercises” later on.
The “Big Picture” contd.
But first … the Big Picture does NOT involve at this
stage worrying about what will be in the exam!
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AI is especially diverse and research-orientated.
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Themes and techniques will unfold throughout the module,
not occur in neat chunks week by week.
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You’ll learn a lot of what you need through the later “serious
exercises” as well as the more free-wheeling ones.
EVERYDAY VISION &
MOVEMENT
Vision Needs in AI
 Seeing what objects are around // where they are // how they’re
moving // etc. … to some degree …
 That degree being dependent on the system’s purposes.
 Seeing what the “affordances” (basically // possibilities of
manipulation) of objects are // even if the objects can’t be
specifically identified.
 Some special things:
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Recognizing faces.
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Recognizing facial expressions // hand gestures // body movements.
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Reading text // mathematical formulas // diagrams // etc.
Seeing What’s in (e.g.) this Room
 Difficulty of seeing where/what even the basic surfaces and edges
are: very noisy // corrupted signal.
 Problem made more complex by shadows // reflections //
transparency // distortion // texture // uneven lighting.
 Ambiguity of component shapes—is it a wheel? Is it a head? Is it an
orange? No … it’s …
 Occlusion of objects.
 Seeing objects from different angles.
 Jointed objects (e.g. // people!) being in different configurations.
 Soft and/or irregular objects such as clothes // crumpled paper.
Moving Around and Performing Actions
Remembering a “mental map” of some sort and knowing
where oneself is in such a map. Keeping track of
movements. Recognizing landmarks.
Creating such a map.
Moving arms // etc. to reach objects efficiently and safely.
Grasping (etc.) objects safely.
(HOT) DRINKS
Case Study
Planning the Delivery of One Drink
Planning the Delivery of One Drink, 1
 Initial Situation: Mike (M) wants beer; Mike is in the sitting
room (S); you are in the kitchen (K); there is an unopened
bottle B of beer in the fridge (F); you are next to F; there is a
bottle-opener O on top of F; doors D-KS, D-KH and DHL[see below] are closed.
 Other Facts:
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F is in K
K and S are connected by door D-KS
K and the hall (H) are connected by door D-KH
H and S are connected by door D-HS.
 Goal Situation (for You to achieve):
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M has B; B is open.
Planning the Delivery of One Drink, 2
Actions available (at a high level):
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agent a opens a bottle b with a bottle-opener o.
agent a opens a door d.
agent a closes a door d.
agent a goes through a room-door e.
agent a moves from (being next to) an object x to an object y.
agent a picks up an object x with one free hand.
agent a picks up an object x with both hands.
agent a puts down an object y.
agent a gives a held object z to agent p.
NB: In most cases you will act as agent a, but we should
be open to other possibilities.
Planning the Delivery of One Drink, 3
Individual Exercise “One-Drink A” [4 mins]
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Write down one sensible sequence of actions that will achieve
the Goal from the Initial Situation. Use only actions from my
list.
Write down another such sequence.
Individual Exercise “One-Drink B” [3 mins]

How did you work out your first sequence, do you think?
Planning the Delivery of One Drink, 4
 One sensible sequence of actions (or rather, action instances) is
as follows…. and is there anything missing?:
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I move to F.
I open F’s door.
I pick up B with one free hand.
I pick up O with one free hand.
I open B with O.
I put down O.
I move to D-KS.
I open D-KS.
I go through D-KS.
I move to M.
I give B to M.
 NB: we instantiated the variables in the action specifications by
replacing them by constants.