CSNB234 ARTIFICIAL INTELLIGENCE. Chapter 6 Knowledge Representation. (Chapter 7, pp. 223-258, Textbook) (Chapter 5, pp. 167-197, Ref. #1). Instructor: Alicia Tang Y. C. Knowledge Representation. Knowledge representation is certainly one of the most important topics
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(Chapter 7, pp. 223-258, Textbook)
(Chapter 5, pp. 167-197, Ref. #1)
Instructor: Alicia Tang Y. C.
Mylopoulos and Levesque (1984) have classified these into four categories
There can be single or multiple attribute facts four categories
There can also be single or multiple value facts .
e.g. Is the barometer pressure rising, falling or steady?
A semantic net that represents a bird’s property four categories
Exercise: four categories
Draw a semantic network for the following description:
Lab is a room. Lab has a door. Lab has many computers.
Printer is in lab. Laser printer is a Printer.
A Disjunctive Net for four categoriesRed or Green Apple
A Conceptual Net that represents “OR”
Conceptual Nets For four categories‘Where do Rivers Flow to’?
A Conjunctive Net for four categoriesblack and white panda
A Conceptual Net that represents “AND”
We shall see this later
are inherited to Bird and
Bird’s properties are
inherited to a bird
species called canary
Sometimes, inheritance may cause problems.
Penguin through inheritance gets the property “fly”.
(in practice it cannot)
To avoid this situation, all the specific properties of a node
must be attached to it through local nodes, so that when an
answer is needed, it will search all the local nodes first. If the answer is not available in the local nodes then the general nodes will be used.
For example if we ask “how does penguin travel?”
the reply will be “it walks” (supposed that already stored in local node)
Title : Qualitative Reasoning
Author : Ken D. Forbus
Publisher : Prentice-Hall
Year : 2000
Converting from Frames to Semantics Nets four categories
(Source: Luger’s AI book)
specialisation of: room
location: the hotel
contains: bed, chair & phone
specialisation of: phone
use: calling room service
billing: through room
contains: mattress, pillow, etc.
IF Age of the student < 21
AND SPM no. of A’s >= 8
THEN Admit the student to BIT
IF the fuel tank is empty
THEN the the car will not start
IF you study hard
AND you study smart
AND you never absent
THEN you will get an “A”
IF the car is dead
THEN check fuel tank
step 1 is complete
IF step 1 is complete
AND the fuel tank is full
THEN check battery
step 2 is complete
IF step 2 is complete
AND the battery is replaced
THEN check electrical fuel lines
IF the spill is liquid
AND the spill pH is < 6
AND the smell is vinegar
THEN the spill material is acetic acid
IF the fuel tank is empty
THEN refuel the car
Short term memory
Long term memory
Question: why are the rules as long term memory?
(the design of the reference engine)
(1) Forward chaining
(2) Backward chaining
Rule 1: IF Y is true
AND D is true
THEN Z is true
Rule 2: IF X is true
AND B is true
AND E is true
THEN Y is true
Rule 3: IF A is true
THEN X is true
Question 1 four categories
Fact 1: A
Fact 2: B
Fact 3: E
What if ‘D’ is also true?
(i.e. as a fact in the KB)
Give the conclusion of the reasoning process.
is done here
Figure: Backward Chaining Example four categories
Formal Logic four categories
Advantages four categories
Easy to understand
Flexible (easy to add or modify)
Hard to follow hierarchies
Poor at representing structured descriptive knowledge
Ineffective search strategy
Not all knowledge can be expressed as rulesProduction Rules
Semantic Networks four categories
Frames four categories
Name some Issues in Knowledge Representation.
Explain your answer.
Give Two advantages and Two disadvantages of Rule-based ES that are NOT listed in this handouts
SUPPLEMENTARY SLIDES four categories
Conflict Resolution four categories
How do we deal with it? IF-part. Thus both of them can be set to fire when the condition part is satisfied.
Methods Used for Conflict Resolution IF-part. Thus both of them can be set to fire when the condition part is satisfied.