Logic and Knowledge Representation K n o w l e d g e r e - - PowerPoint PPT Presentation

logic and knowledge representation
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Logic and Knowledge Representation K n o w l e d g e r e - - PowerPoint PPT Presentation

Logic and Knowledge Representation K n o w l e d g e r e p r e s e n t a t i o n , O n t o l o g i e s , S e m a n t i c We b 2 4 M a y 2 0 1 7 g s i l e n o @e n s t . f r G i


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SLIDE 1

Logic and Knowledge Representation

G i

  • v

a n n i S i l e n

  • g

s i l e n

  • @e

n s t . f r

T é l é c

  • m

P a r i s T e c h , P a r i s

  • D

a u p h i n e U n i v e r s i t y

K n

  • w

l e d g e r e p r e s e n t a t i

  • n

, O n t

  • l
  • g

i e s , S e m a n t i c We b

2 4 M a y 2 1 7

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SLIDE 2

What is Knowledge?

  • K

n

  • w

l e d g e i s w h a t w e a s c r i b e t

  • a

n a g e n t t

  • p

r e d i c t h i s b e h a v i

  • u

r u s i n g p r i n c i p l e s

  • f

r a t i

  • n

a l i t y . e x a m p l e

  • f

r a t i

  • n

a l i t y p r i n c i p l e : I f a c

  • u

r s e

  • f

a c t i

  • n

l e a d t

  • m

y g

  • a

l , I w i l l t a k e t h a t c

  • u

r s e

  • f

a c t i

  • n

. N

  • t

e : k n

  • w

l e d g e r e p r e s e n t a t i

  • n
  • n

l y r e p r

  • d

u c e s t h a t w h i c h w e a s c r i b e ; i t i s n

  • t

i n t e n d e d t

  • b

e a c c u r a t e , p h y s i c a l m

  • d

e l

N e w e l l , A . ( 1 9 8 2 ) . T h e K n

  • w

l e d g e L e v e l . A r t i fj c i a l I n t e l l i g e n c e , 1 8 ( 1 ) , 8 7 – 1 2 7 .

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SLIDE 3

Data, Information, Knowledge

  • D

a t a : u n i n t e r p r e t e d s i g n a l s

  • r

s y m b

  • l

s

  • I

n f

  • r

m a t i

  • n

: d a t a w i t h a d d e d m e a n i n g

  • K

n

  • w

l e d g e : a l l d a t a a n d i n f

  • r

m a t i

  • n

t h a t p e

  • p

l e u s e t

  • a

c t , a c c

  • m

p l i s h t a s k s a n d t

  • c

r e a t e n e w i n f

  • r

m a t i

  • n

( k n

  • w
  • h
  • w

,

  • w

h y ,

  • w

h

  • ,
  • w

h e r e a n d

  • w

h e n ) .

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SLIDE 4

Data, Information, Knowledge

D a t a : . . .

  • .

. . I n f

  • r

m a t i

  • n

: i t i s a m e s s a g e s a y i n g S O S K n

  • w

l e d g e : e m e r g e n c y s i g n a l , s t a r t r e s c u e

  • p

e r a t i

  • n

. D a t a : 1 4 5 4 3 1 2 I n f

  • r

m a t i

  • n

: i t i s a t e l e p h

  • n

e n u m b e r

  • f

a p e r s

  • n

K n

  • w

l e d g e : t

  • m

a k e a n a p p

  • i

n t m e n t I n e e d t

  • c

a l l i t

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SLIDE 5

Types of knowledge

  • I

m p l i c i t ,

  • f

t e n n

  • t

c

  • n

s c i

  • u

s , i n t e r n a l

  • E

x p l i c i t , c

  • n

s c i

  • u

s a n d e x t e r n a l

  • T

a c i t , i n c

  • n

t r a s t t

  • w

h a t i s i n f

  • c

u s ( P

  • l

a n y i )

P i c t u r e f r

  • m

B r

  • h

m , R . ( 2 7 ) . B r i n g i n g P

  • l

y a n i

  • n

t h e T h e a t r e S t a g e

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SLIDE 6

More types of knowledge

  • P

r

  • c

e d u r a l k n

  • w

l e d g e : p r

  • c

e d u r e s , p l a n s

  • D

e c l a r a t i v e k n

  • w

l e d g e : c

  • n

c e p t s ,

  • b

j e c t s , f a c t s

  • H

e u r i s t i c k n

  • w

l e d g e : e x p e r i e n c e , d e f a u l t s

  • K

n

  • w

l e d g e a b

  • u

t u n c e r t a i n t y : p r

  • b

a b i l i t y e s t i m a t i

  • n

s , d e f a u l t s , k n

  • w

i n g w h a t y

  • u

k n

  • w
  • C
  • m

m

  • n
  • s

e n s e k n

  • w

l e d g e : g l

  • b

a l c

  • n

c e p t s a n d t h e

  • r

i e s , g e n e r a l h i e r a r c h i e s

  • Me

t a

  • k

n

  • w

l e d g e : k n

  • w

l e d g e a b

  • u

t k n

  • w

l e d g e t y p e s a n d t h e i r u s e

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SLIDE 7

What is Knowledge Representation?

  • s

u r r

  • g

a t e

  • e

x p r e s s i

  • n
  • f
  • n

t

  • l
  • g

i c a l c

  • m

m i t m e n t

  • t

h e

  • r

y

  • f

i n t e l l i g e n t r e a s

  • n

i n g

  • m

e d i u m

  • f

e ffj c i e n t c

  • m

p u t a t i

  • n
  • m

e d i u m

  • f

h u m a n e x p r e s s i

  • n

R . D a v i s , H . S h r

  • b

e , a n d P . S z

  • l
  • v

i t s . Wh a t i s a K n

  • w

l e d g e R e p r e s e n t a t i

  • n

? A I M a g a z i n e , 1 4 ( 1 ) : 1 7

  • 3

3 , 1 9 9 3 . h t t p : / / g r

  • u

p s . c s a i l . m i t . e d u / m e d g / f t p / p s z / k

  • r

e p . h t m l

a s i m p l i fj e d r e p r e s e n t a t i

  • n

r e i f y i n g

  • u

r a t t e n t i

  • n

t

  • t

h e w

  • r

l d a n d a m

  • d

e l

  • f

a s s

  • c

i a t e d r e a s

  • n

i n g p r

  • c

e s s e s t h a t i s a c c e s s i b l e t

  • p

r

  • g

r a m s a n d t

  • p

e

  • p

l e

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SLIDE 8

Knowledge systems

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SLIDE 9

if flower and seed then phanerogam if phanerogam and bare-seed then fir if phanerogam and 1-cotyledon then monocotyledonous if phanerogam and 2-cotyledon then dicotyledonous if monocotyledon and rhizome then thrush if dicotyledon then anemone if monocotyledon and ¬rhizome then lilac if leaf and flower then cryptogamous if cryptogamous and ¬root then foam if cryptogamous and root then fern if ¬leaf and plant then thallophyte if thallophyte and chlorophyll then algae if thallophyte and ¬ chlorophyll then fungus if ¬leaf and ¬flower and ¬plant then colibacille

Example of expert system

rhizome + flower + seed + 1-cotyledon ?

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SLIDE 10

From expert systems to KBS

  • E

x p e r t s y s t e m s S e p a r a t e k n

  • w

l e d g e ( r u l e s ) f r

  • m

t h e r e a s

  • n

i n g e n g i n e

  • K

n

  • w

l e d g e

  • b

a s e d s y s t e m s S e p a r a t e k n

  • w

l e d g e ( c

  • n

c e p t s ) f r

  • m

r u l e s a n d r e a s

  • n

i n g

– e

x a m p l e : F r a m e s

  • s

t e r e

  • t

y p e d s t r u c t u r e s

  • f

k n

  • w

l e d g e

– e

x a m p l e : S e m a n t i c n e t w

  • r

k s

  • r

e p r e s e n t a t i

  • n

b y g r a p h

  • b

a s e d f

  • r

m a l i s m

  • m
  • d

e l e n t i t i e s a n d t h e i r r e l a t i

  • n

s

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SLIDE 11

Frames

  • F

r a m e s a r e " s t e r e

  • t

y p e d " k n

  • w

l e d g e u n i t s r e p r e s e n t i n g s i t u a t i

  • n

s ,

  • b

j e c t s

  • r

e v e n t s

  • r

( c l a s s e s ) s e t s

  • f

s u c h e n t i t i e s .

  • A

f r a m e i s a c

  • l

l e c t i

  • n
  • f

a t t r i b u t e s ( s l

  • t

s ) , s p e c i fj e d b y f a c e t s t h a t c

  • r

r e s p

  • n

d t

  • t

h e v a l u e s t h e y a c q u i r e

  • r

p r

  • c

e d u r e s t h a t l a u n c h .

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SLIDE 12

“ Wi l l y t h r e w a b a l l t

  • M
  • r

g a n . ”

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SLIDE 13

“ Wi l l y t h r e w a b a l l t

  • M
  • r

g a n . ” n

  • d

e s : e n t i t i e s a r c s : r e l a t i

  • n

s h i p s

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SLIDE 14

“ Wi l l y t h r e w a b a l l t

  • M
  • r

g a n . ” n

  • d

e s : e n t i t i e s a r c s : r e l a t i

  • n

s h i p s l a b e l s

  • n

n

  • d

e s : e n t i t y n a m e s l a b e l s

  • n

a r c s : r e l a t i

  • n

n a m e s

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SLIDE 15

“ Wi l l y t h r e w a b a l l t

  • M
  • r

g a n . ”

fact( throwing, actor, willy ). % or: throwing( actor, willy ). fact( throwing, receiver, morgan ). % or: throwing( receiver, morgan ). fact( throwing, object, ball ). % or: throwing( object, ball ). who_action_what( Who, Act, What) :- fact( Act, actor, Who ), fact( Act, object, What ). ?- fact( throwing, X, willy). ?- who_action_what(willy, throwing, ball).

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SLIDE 16

“ Wi l l y t h r e w a b a l l t

  • M
  • r

g a n . ”

fact( throwing, actor, willy ). % or: throwing( actor, willy ). fact( throwing, receiver, morgan ). % or: throwing( receiver, morgan ). fact( throwing, object, ball ). % or: throwing( object, ball ). who_action_what( Who, Act, What) :- fact( Act, actor, Who ), fact( Act, object, What ). ?- fact( throwing, X, willy). ?- who_action_what(willy, throwing, ball).

We n e e d m

  • r

e k n

  • w

l e d g e t

  • i

n f e r s

  • m

e t h i n g m

  • r

e i n t e r e s t i n g !

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SLIDE 17

Semantic Networks

K n

  • w

l e d g e s y s t e m s , i n s p i r e d b y h u m a n c

  • g

n i t i

  • n

, a i m t

  • b

e r e u s a b l e a n d e ffj c i e n t . . .

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SLIDE 18

Semantic Networks

. . . b u t w h a t t h e m a c h i n e r e a d s i s n

  • t

w h a t w e r e a d !

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SLIDE 19

Semantic Networks

A n n

  • t

a t i

  • n

p r i n c i p l e : d i fg e r e n c e s i n i n t e n d e d p r

  • c

e s s i n g s h

  • u

l d b e r e fm e c t e d i n d i fg e r e n c e s i n t h e s y m b

  • l

s t r u c t u r e s

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SLIDE 20

First encounter between semantic networks and logic: KL-ONE

P r i m i t i v e c

  • n

c e p t s ( * ) d

  • n
  • t

h a v e s u ffj c i e n t c

  • n

d i t i

  • n

s , m a y h a v e n e c e s s a r y D e r i v e d c

  • n

c e p t s s p e c i fj e d b y s u ffj c i e n t a n d n e c e s s a r y c

  • n

d i t i

  • n

s .

B r a c h m a n , R . J . , & S c h m

  • l

z e , J . ( 1 9 8 5 ) . A n O v e r v i e w

  • f

t h e K L

  • O

N E K n

  • w

l e d g e R e p r e s e n t a t i

  • n

S y s t e m . C

  • g

n i t i v e S c i e n c e , 9 , 1 7 1 – 2 1 6 .

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SLIDE 21

First encounter between semantic networks and logic: KL-ONE

B r a c h m a n , R . J . , & S c h m

  • l

z e , J . ( 1 9 8 5 ) . A n O v e r v i e w

  • f

t h e K L

  • O

N E K n

  • w

l e d g e R e p r e s e n t a t i

  • n

S y s t e m . C

  • g

n i t i v e S c i e n c e , 9 , 1 7 1 – 2 1 6 . A MESSAGE is a THING with at least one Sender, all of which are PERSONs, at least one Recipient, all of which are PERSONs, exactly one Body, which is a TEXT, exactly one SendDate, which is a DATE, and exactly one ReceivedDate, which is a DATE.

v / r : v a l u e r e s t r i c t i

  • n

n / r : n u m b e r r e s t r i c t i

  • n

( m i n , m a x ) , N I L = ∞

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SLIDE 22

First encounter between semantic networks and logic: KL-ONE

B r a c h m a n , R . J . , & S c h m

  • l

z e , J . ( 1 9 8 5 ) . A n O v e r v i e w

  • f

t h e K L

  • O

N E K n

  • w

l e d g e R e p r e s e n t a t i

  • n

S y s t e m . C

  • g

n i t i v e S c i e n c e , 9 , 1 7 1 – 2 1 6 . A STARFLEET-MESSAGE is a MESSAGE, all of whose Senders are STARFLEET-COMMANDERS.

r

  • l

e r e s t r i c t i

  • n

t h r

  • u

g h v / r

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SLIDE 23

First encounter between semantic networks and logic: KL-ONE

  • K

L

  • O

N E i s a n a u t

  • m

a t i c c l a s s i fj e r

– t

a k e s a n e w C

  • n

c e p t a n d a u t

  • m

a t i c a l l y d e t e r m i n e s a l l s u b s u m p t i

  • n

r e l a t i

  • n

s ( i s

  • a

) b e t w e e n i t a n d a l l

  • t

h e r C

  • n

c e p t s i n t h e n e t w

  • r

k

– a

d d s n e w l i n k s w h e n n e w s u b s u m p t i

  • n

r e l a t i

  • n

s a r e d i s c

  • v

e r e d

– a

u t

  • m

a t e s t h e p l a c e m e n t

  • f

n e w C

  • n

c e p t s i n t h e t a x

  • n
  • m

y

– I

t i s s

  • u

n d ( a l l f

  • u

n d s u b s u m p t i

  • n

r e l a t i

  • n

s a r e l e g i t i m a t e ) b u t n

  • t

c

  • m

p l e t e ( i t d

  • e

s n

  • t

fj n d a l l s u b s u m p t i

  • n

r e l a t i

  • n

s )

  • b

a s i s f

  • r

O WL ( g i v i n g s e m a n t i c s t

  • t

h e S e m a n t i c We b )

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SLIDE 24

Differences

P r

  • l
  • g

s p e c i a l p u r p

  • s

e r e a s

  • n

i n g e n g i n e

– c

l

  • s

e d w

  • r

l d a s s u m p t i

  • n

– n

e g a t i

  • n

a s f a i l u r e ( N A F )

– o

n l y s u ffj c i e n t c

  • n

d i t i

  • n

s

– n

  • t

r u e e x i s t e n t i a l

– q

u a n t i fj c a t i

  • n

– p

r

  • g

r a m m e r p r e v e n t s i n fj n i t e l

  • p

s K L

  • O

N E a n d O WL g e n e r a l p u r p

  • s

e k n

  • w

l e d g e m a n i p u l a t i

  • n

– o

p e n w

  • r

l d a s s u m p t i

  • n

– n

  • r

s t r

  • n

g n e g a t i

  • n

– a

t l e a s t n e c e s s a r y ,

  • p

t i

  • n

a l l y s u ffj c i e n t c

  • n

d i t i

  • n

s

– i

n fj n i t e l

  • p

s s h

  • u

l d n

  • t

b e p

  • s

s i b l e

– l

e s s e x p r e s s i v e

slide-25
SLIDE 25

Qualifications of KR

slide-26
SLIDE 26

Canonicity

  • A

K R f

  • r

m a l i s m i s c a n

  • n

i c i f

  • n

e p i e c e

  • f

k n

  • w

l e d g e c a n

  • n

l y b e r e p r e s e n t e d i n

  • n

e w a y

alive(Elvis). is(Elvis, alive). alive(elvis). alive(Elvis, true). vivant(Elvis).

  • C

a n

  • n

i c i t y i s i m p r

  • v

e d b y

– r

e s t r i c t i n g t h e f

  • r

m a l i s m ( e . g .

  • n

l y u n a r y p r e d i c a t e s )

– p

r

  • v

i d i n g g u i d e l i n e s ( e . g . p r

  • p

e r n a m e i n u p p e r c a s e )

– u

s i n g s t a n d a r d v

  • c

a b u l a r i e s ( e . g . { a l i v e , d e a d } )

slide-27
SLIDE 27

Expressiveness

  • A

K R f

  • r

m a l i s m i s m

  • r

e e x p r e s s i v e t h a n a n

  • t

h e r

  • n

e i f w e c a n s a y t h i n g s i n t h e fj r s t f

  • r

m a l i s m t h a t w e c a n n

  • t

s a y i n t h e s e c

  • n

d . F i r s t O r d e r L

  • g

i c > P r

  • p
  • s

i t i

  • n

a l L

  • g

i c ∀x : m a n ( x )

m

  • r

t a l ( x ) ?

slide-28
SLIDE 28

Decidability

  • A

K R f

  • r

m a l i s m i s d e c i d a b l e , i f t h e r e i s a n a l g

  • r

i t h m t h a t c a n a n s w e r a n y q u e r y

  • n

a k n

  • w

l e d g e b a s e i n t h a t f

  • r

m a l i s m .

  • T

y p i c a l l y , t h e m

  • r

e e x p r e s s i v e a f

  • r

m a l i s m , t h e m

  • r

e l i k e l y i t i s u n d e c i d a b l e .

slide-29
SLIDE 29

Decidability

  • A

K R f

  • r

m a l i s m i s d e c i d a b l e , i f t h e r e i s a n a l g

  • r

i t h m t h a t c a n a n s w e r a n y q u e r y

  • n

a k n

  • w

l e d g e b a s e i n t h a t f

  • r

m a l i s m .

  • A

f

  • r

m a l i s m c a n b e m a d e d e c i d a b l e b y r e s t r i c t i n g i t .

– p

r

  • p
  • s

i t i

  • n

a l l

  • g

i c i s d e c i d a b l e

– F

O L i s d e c i d a b l e i f a l l f

  • r

m u l a s a r e i n t h i s f

  • r

m : ∃x , y , … . z , q , … ∀ : p ( x , y ) … = > … e x i s t e n t i a l u n i v e r s a l a r b i t r a r y f

  • r

m u l a q u a n t i fj e r s q u a n t i fj e r s w i t h

  • u

t q u a n t i fj e r s

slide-30
SLIDE 30

Closed and Open World Assumptions

  • A

K R f

  • r

m a l i s m f

  • l

l

  • w

s t h e c l

  • s

e d w

  • r

l d a s s u m p t i

  • n

( C WA ) , i f a n y s t a t e m e n t t h a t c a n n

  • t

b e p r

  • v

e n i s a s s u m e d t

  • b

e f a l s e .

  • S
  • m

e t i m e s t h e

  • p

e n w

  • r

l d a s s u m p t i

  • n

( O WA ) i s m

  • r

e a p p r

  • p

r i a t e . A s t a t e m e n t c a n t h e n b e :

– p

r

  • v

a b l e f a l s e

– p

r

  • v

a b l e t r u e

– u

n k n

  • w

n

slide-31
SLIDE 31

Unique Name Assumption (UNA)

  • A

K R f

  • r

m a l i s m f

  • l

l

  • w

s t h e u n i q u e n a m e a s s u m p t i

  • n

( U N A ) , i f d i fg e r e n t n a m e s a l w a y s r e f e r t

  • d

i fg e r e n t

  • b

j e c t s .

  • T

h e U N A i s n

  • t

u s e f u l i f d i fg e r e n t p e

  • p

l e w a n t t

  • u

s e d i fg e r e n t i d e n t i fj e r s .

slide-32
SLIDE 32

Schemas

  • A

K R f

  • r

m a l i s m i s s c h e m a

  • b
  • u

n d , i f

  • n

e h a s t

  • d

e c i d e u p f r

  • n

t w h i c h e n t i t i e s c a n h a v e w h i c h p r

  • p

e r t i e s .

  • P

r

  • l
  • g

i s s c h e m a

  • f

r e e , a n y e n t i t y c a n h a v e a n y p r

  • p

e r t y .

  • I

n s c h e m a

  • b
  • u

n d f

  • r

m a l i s m s ,

  • n

e h a s t

  • d

e c i d e a p r i

  • r

i f

  • r

c l a s s e s

  • f

t h i n g s a n d t h e i r p r

  • p

e r t i e s : a s c h e m a

  • b
  • u

n d f

  • r

m a l i s m p u t s m

  • r

e m

  • d

e l i n g c

  • n

s t r a i n t s , b u t c a n e x c l u d e n

  • n
  • s

e n s i b l e s t a t e m e n t s .

slide-33
SLIDE 33

Schemas

  • D

a t a b a s e s a r e a p a r t i c u l a r s c h e m a

  • b
  • u

n d K R f

  • r

m a l i s m .

  • A

d a t a b a s e c a n b e s e e n a s a s e t

  • f

t a b l e s .

Name Profession Birth Elvis Singer 1935 Obama President 1961 … … … Name Resolution Brand Sony T300 4 MP Sony Ixus700 12 MP Canon … … …

e a c h r

  • w

c

  • r

r e s p

  • n

d s t

  • a

t h i n g e a c h t a b l e c

  • r

r e s p

  • n

d s t

  • n

e c l a s s

  • f

t h i n g s e a c h c

  • l

u m n c

  • r

r e s p

  • n

d s t

  • a

p r

  • p

e r t y

slide-34
SLIDE 34

Inheritance

  • A

K R f

  • r

m a l i s m s u p p

  • r

t s i n h e r i t a n c e , i f p r

  • p

e r t i e s s p e c i fj e d f

  • r
  • n

e c l a s s

  • f

t h i n g s c a n b e a u t

  • m

a t i c a l l y t r a n s f e r r e d t

  • a

m

  • r

e s p e c i fj c c l a s s .

  • A

c l a s s i s a s e t

  • f

e n t i t i e s w i t h t h e s a m e p r

  • p

e r t i e s .

P e r s

  • n

Name Profession Birth S i n g e r Name Profession Birth Instrument m

  • r

e g e n e r a l c l a s s , f e w p r

  • p

e r t i e s m

  • r

e s p e c i fj c c l a s s , m

  • r

e p r

  • p

e r t i e s , s

  • m

e r e s t r i c t i

  • n

s : = s i n g e r i n h e r i t e d p r

  • p

e r t i e s a d d i t i

  • n

a l p r

  • p

e r t i e s r e s t r i c t i

  • n

i n h e r i t a n c e / s u b c l a s s r e l a t i

  • n

s h i p

slide-35
SLIDE 35

Monotonicity and non-monotonicity

  • A

K R f

  • r

m a l i s m i s m

  • n
  • t
  • n

i c , i f a d d i n g n e w k n

  • w

l e d g e d

  • e

s n

  • t

u n d

  • d

e d u c e d f a c t s .

  • F

i r s t

  • r

d e r l

  • g

i c a n d p r

  • p
  • s

i t i

  • n

a l l

  • g

i c a r e m

  • n
  • t
  • n

i c .

  • M
  • n
  • t
  • n

i c i t y c a n b e c

  • u

n t e r

  • i

n t u i t i v e . I t r e q u i r e s t

  • k

n

  • w

e v e r y t h i n g u p f r

  • n

t .

elvis_is_person elvis_is_alive elvis_is_dead => ~ elvis_is_alive

+

=> elvis_is_alive elvis_is_person elvis_is_alive elvis_is_dead => ~ elvis_is_alive elvis_is_dead => michael_jackson_alive => elvis_is_dead

⊆ ⊆

=> elvis_is_alive

slide-36
SLIDE 36
  • A

K R f

  • r

m a l i s m i s m

  • n
  • t
  • n

i c , i f a d d i n g n e w k n

  • w

l e d g e d

  • e

s n

  • t

u n d

  • d

e d u c e d f a c t s .

  • D

e f a u l t l

  • g

i c i s n

  • t

m

  • n
  • t
  • n

i c .

elvis_is_person: elvis_is_alive elvis_is_alive => elvis_is_alive elvis_is_dead ~elvis_is_alive if Elvis is a person (and nothing says he’s not alive) then he is alive if Elvis is dead then he is not alive elvis_is_person elvis_is_dead

+

prerequisite conclusion justification

Monotonicity and non-monotonicity

slide-37
SLIDE 37
  • A

K R f

  • r

m a l i s m i s d i s t r i b u t e d , i f i t e n c

  • u

r a g e s u s e a n d c

  • p

e r a t i

  • n

b y d i fg e r e n t p e

  • p

l e / s y s t e m s a c r

  • s

s d i fg e r e n t p l a c e s /

  • r

g a n i z a t i

  • n

s .

Distributedness

slide-38
SLIDE 38

Semantic Web

slide-39
SLIDE 39

What's in a web page?

  • T

e x t u a l c

  • n

t e n t , m a r k u p a n d e m b e d d e d m e d i a

  • T

h e t y p i c a l m a r k u p c

  • n

s i s t s

  • f

:

– h

y p e r

  • l

i n k s t

  • r

e l a t e d c

  • n

t e n t ,

– r

e n d e r i n g i n f

  • r

m a t i

  • n

( p a g i n a t i

  • n

, f

  • n

t s i z e a n d c

  • l
  • u

r , … )

  • T

h e s e m a n t i c c

  • n

t e n t i s a c c e s s i b l e t

  • h

u m a n s b u t n

  • t

d i r e c t l y t

  • c
  • m

p u t e r s . . .

slide-40
SLIDE 40

The Web was designed as an information space, with the goal that it

should be useful not only for human-human communication, but also that machines would be able to participate and help.

One of the major obstacles to this has been the fact that most information on the Web is designed for human consumption, and even if it was derived from a database with well

defined meanings (in at least some terms) for its columns, that the structure of the data is not evident to a robot browsing the Web. Leaving aside the artificial intelligence problem of training machines to behave like people, the Semantic Web approach instead develops

languages for expressing information in a machine processable form.

T i m B e r n e r s

  • L

e e , T h e S e m a n t i c We b R

  • a

d m a p .

slide-41
SLIDE 41
  • E

x t e r n a l a g r e e m e n t

  • n

m e a n i n g

  • f

a n n

  • t

a t i

  • n

s

– P

r

  • b

l e m s w i t h t h i s a p p r

  • a

c h

  • I

n fm e x i b l e

  • L

i m i t e d n u m b e r

  • f

t h i n g s c a n b e e x p r e s s e d

  • U

s e f

  • r

m a l v

  • c

a b u l a r i e s

  • r
  • n

t

  • l
  • g

i e s t

  • s

p e c i f y m e a n i n g

  • f

a n n

  • t

a t i

  • n

s

– o

n t

  • l
  • g

i e s p r

  • v

i d e a v

  • c

a b u l a r y

  • f

t e r m s t h a t a r e m a c h i n e u n d e r s t a n d a b l e

– n

e w t e r m s c a n b e f

  • r

m e d b y c

  • m

b i n i n g e x i s t i n g

  • n

e s a s a k i n d

  • f

“ c

  • n

c e p t u a l L e g

– m

e a n i n g ( s e m a n t i c s )

  • f

s u c h t e r m s i s f

  • r

m a l l y s p e c i fj e d

How to add meaning for machines?

slide-42
SLIDE 42

Four principles towards a Semantic Web of Data

  • P

1 : g i v e a l l t h i n g s a n a m e

slide-43
SLIDE 43

Four principles towards a Semantic Web of Data

  • P

2 : r e l a t i

  • n

s h i p s f

  • r

m a g r a p h b e t w e e n t h i n g s ( a k n

  • w

l e d g e g r a p h )

slide-44
SLIDE 44

Four principles towards a Semantic Web of Data

  • P

3 : n a m e s a r e a d d r e s s e s

  • n

t h e We b

slide-45
SLIDE 45
  • P

1 + P 2 + P 3 : a h u g e g l

  • b

a l g r a p h

L i n k i n g

  • p

e n d a t a c l

  • u

d d i a g r a m : h t t p : / / l

  • d
  • c

l

  • u

d . n e t /

slide-46
SLIDE 46

Four principles towards a Semantic Web of Data

  • P

4 : g i v e e x p l i c i t , f

  • r

m a l s e m a n t i c s

– a

s s i g n t y p e s t

  • t

h i n g s

– a

s s i g n t y p e s t

  • r

e l a t i

  • n

s

– o

r g a n i z e t y p e s i n h i e r a r c h i e s

– s

p e c i f y c

  • n

s t r a i n t s

slide-47
SLIDE 47

Semantic Web

  • T

h e S e m a n t i c We b i s a n e v

  • l

v i n g e x t e n s i

  • n
  • f

t h e Wo r l d Wi d e We b , p r

  • m
  • t

i n g a d i s t r i b u t e d k n

  • w

l e d g e r e p r e s e n t a t i

  • n

.

  • I

t p r

  • v

i d e s s t a n d a r d s t

  • – i

d e n t i f y e n t i t i e s ( U R I s )

– e

x p r e s s f a c t s ( R D F )

– e

x p r e s s c

  • n

c e p t s ( R D F S )

– s

h a r e v

  • c

a b u l a r i e s

– r

e a s

  • n
  • n

f a c t s ( O WL )

  • T

h e s e s t a n d a r d s a r e p r

  • d

u c e d a n d e n d

  • r

s e d b y t h e Wo r d Wi d e We b C

  • n

s

  • r

t i u m ( W3 C )

slide-48
SLIDE 48

The Semantic Web Tower

slide-49
SLIDE 49

URI and namespaces

  • U

R I = u n i f

  • r

m r e s

  • u

r c e s i d e n t i fj e r

– u

n i f

  • r

m r e s

  • u

r c e n a m e s ( U R N s ) : U R I s u s e d t

  • n

a m e s

  • m

e t h i n g , e v e n i f t h i s i s a n a b s t r a c t

  • b

j e c t t h a t i s n

  • t

a v a i l a b l e

  • n

t h e We b .

  • f
  • r

i n s t a n c e , a p e r s

  • n

m i g h t h a v e a U R I t h a t i s u s e d i n

  • n

t

  • l
  • g

i e s t

  • r

e f e r t

  • t

h a t p e r s

  • n

.

– u

n i f

  • r

m r e s

  • u

r c e l

  • c

a t

  • r

s ( U R L s ) : U R I s u s e d t

  • s

p e c i f y t h e l

  • c

a t i

  • n
  • f

s

  • m

e t h i n g . t h e y s t a r t w i t h a p r

  • t
  • c
  • l

i d e n t i fj e r , w i t h a w e l l

  • e

s t a b l i s h e d t e c h n i c a l i n t e r p r e t a t i

  • n

( e . g . " h t t p " ) .

slide-50
SLIDE 50

URI and namespaces

  • N

a m e s p a c e s

– D

e r i v e d f r

  • m

d

  • m

a i n r e g i s t r a t i

  • n

( e p i t a . f r )

– E

v e r y t h i n g u p t

  • #

m a y b e n a m e s p a c e

  • E

x a m p l e s : u r n : m y a p p n a m e : s t u d e n t s # s t u d e n t 1 2 3 4 h t t p : / / m y s e r v e r . c

  • m

/ m y a p p / s t u d e n t s / s t u d e n t 1 2 3 4

  • U

R I a r e d e r e f e r e n c i a b l e i f t h e r e s

  • u

r c e i d e n t i fj e d b y t h e U R I i s r e t r i e v a b l e f r

  • m

t h a t U R I

slide-51
SLIDE 51

RDF (resource description framework)

  • R

D F i s a d a t a m

  • d

e l :

– a

p p l i c a t i

  • n

a n d d

  • m

a i n i n d e p e n d e n t

– b

a s e d

  • n

s i m p l e t r i p l e f

  • r

m a t

– (

l a b e l e d a n d d i r e c t e d ) g r a p h

slide-52
SLIDE 52

RDF (resource description framework)

  • R

D F i s a d a t a m

  • d

e l :

– a

p p l i c a t i

  • n

a n d d

  • m

a i n i n d e p e n d e n t

– b

a s e d

  • n

s i m p l e t r i p l e f

  • r

m a t

– (

l a b e l e d a n d d i r e c t e d ) g r a p h

  • R

D F “ s t a t e m e n t s ” c

  • n

s i s t

  • f

– r

e s

  • u

r c e s ( = n

  • d

e s )

  • w

h i c h h a v e p r

  • p

e r t i e s

– w

h i c h h a v e v a l u e s ( = n

  • d

e s , s t r i n g s , . . . )

slide-53
SLIDE 53

RDF (resource description framework)

  • R

D F i s a d a t a m

  • d

e l :

– a

p p l i c a t i

  • n

a n d d

  • m

a i n i n d e p e n d e n t

– b

a s e d

  • n

s i m p l e t r i p l e f

  • r

m a t

– (

l a b e l e d a n d d i r e c t e d ) g r a p h

  • R

D F “ s t a t e m e n t s ” c

  • n

s i s t

  • f

– r

e s

  • u

r c e s ( = n

  • d

e s )

  • w

h i c h h a v e p r

  • p

e r t i e s

– w

h i c h h a v e v a l u e s ( = n

  • d

e s , s t r i n g s ) p r e d i c a t e ( s u b j e c t ,

  • b

j e c t ) s u b j e c t p r e d i c a t e

  • b

j e c t

slide-54
SLIDE 54

RDF (resource description framework)

slide-55
SLIDE 55

RDF and XML

  • B

e i n g s

  • g

e n e r a l , s y n t a c t i c d e t a i l s a r e r e l a t i v e l y i n s i g n i fj c a n t ; h

  • w

e v e r X M L i s a n e x a m p l e d

  • f

u s e d s y n t a c t i c s t r u c t u r e .

  • N

O T E : X M L i s j u s t a w a y t

  • w

r i t e a n d t r a n s p

  • r

t R D F , b u t i s n

  • t

a c

  • m

p

  • n

e n t

  • f

R D F !

  • R

D F d a t a c a n a l s

  • b

e s t

  • r

e d v e r y d i fg e r e n t l y , f

  • r

e x a m p l e i n a r e l a t i

  • n

a l d a t a b a s e

.

slide-56
SLIDE 56

RDF, a note on resources

  • A

g r a p h n

  • d

e ( c

  • r

r e s p

  • n

d i n g t

  • a

r e s

  • u

r c e ) c a n b e

– t

h e v a l u e

  • f

a p r

  • p

e r t y

– a

r b i t r a r i l y c

  • m

p l e x t r e e a n d g r a p h s t r u c t u r e s

  • S

y n t a c t i c a l l y , v a l u e s c a n b e

– e

m b e d d e d ( i . e . l e x i c a l l y i n

  • l

i n e )

– o

r r e f e r e n c e d ( l i n k e d )

slide-57
SLIDE 57

RDF Schema

  • B

a s e

  • l

e v e l s p e c i fj c a t i

  • n
  • f

s e m a n t i c s

  • L

a n g u a g e c

  • n

s t r u c t s i n c l u d e :

– c

l a s s ,

– p

r

  • p

e r t y ,

– s

u b c l a s s ,

– s

u b p r

  • p

e r t y

  • C

l a s s e s a n d p r

  • p

e r t i e s a r e t h e m s e l v e s a l s

  • r

e s

  • u

r c e s : e n a b l e s a n n

  • t

a t i

  • n

s a b

  • u

t a n n

  • t

a t i

  • n

s

  • V
  • c

a b u l a r y c a n b e u s e d t

  • d

e fj n e

  • t

h e r v

  • c

a b u l a r i e s f

  • r

y

  • u

r a p p l i c a t i

  • n

d

  • m

a i n

slide-58
SLIDE 58

RDF(S) Terminology and Semantics

  • C

l a s s e s a n d c l a s s h i e r a r c h y

– A

l l c l a s s e s a r e i n s t a n c e s

  • f

r d f s : C l a s s

– A

c l a s s h i e r a r c h y i s d e fj n e d b y r d f s : s u b C l a s s O f

  • I

n s t a n c e s ( i n d i v i d u a l s )

  • f

a c l a s s

– d

e fj n e d b y r d f : t y p e

slide-59
SLIDE 59

RDF(S) Terminology and Semantics

  • P

r

  • p

e r t i e s

– p

r

  • p

e r t i e s a r e g l

  • b

a l : a p r

  • p

e r t y n a m e i n

  • n

e p l a c e i s t h e s a m e a s t h e p r

  • p

e r t y n a m e i n a n

  • t

h e r ( a s s u m i n g t h e s a m e n a m e s p a c e )

– p

r

  • p

e r t i e s f

  • r

m a h i e r a r c h y , r d f s : s u b P r

  • p

e r t y O f

  • D
  • m

a i n a n d R a n g e

  • f

a p r

  • p

e r t y

– d

  • m

a i n : t h e c l a s s (

  • r

c l a s s e s ) t h a t h a v e t h e p r

  • p

e r t y

– r

a n g e : t h e c l a s s (

  • r

c l a s s e s ) t

  • w

h i c h p r

  • p

e r t y v a l u e s b e l

  • n

g

slide-60
SLIDE 60

RDF(S) Terminology and Semantics

slide-61
SLIDE 61

RDF(S) Terminology and Semantics

E x a m p l e :

(ex:MotorVehicle, rdf:type, rdfs:Class) (ex:PassengerVehicle, rdf:type, rdfs:Class) (ex:Van, rdf:type, rdfs:Class) (ex:Truck, rdf:type, rdfs:Class) (ex:MiniVan, rdf:type, rdfs:Class) (ex:PassengerVehicle, rdfs:subClassOf, ex:MotorVehicle) (ex:Van, rdfs:subClassOf, ex:MotorVehicle) (ex:Truck, rdfs:subClassOf, ex:MotorVehicle) (ex:MiniVan, rdfs:subClassOf, ex:Van) (ex:MiniVan, rdfs:subClassOf, ex:PassengerVehicle)

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SLIDE 62

Querying RDF: SPARQL

  • S

i m p l e P r

  • t
  • c
  • l

A n d R D F Q u e r y L a n g u a g e

– W3

C s t a n d a r d i s a t i

  • n

e fg

  • r

t s i m i l a r t

  • t

h e X Q u e r y

– q

u e r y l a n g u a g e f

  • r

X M L d a t a

– s

u i t a b l e f

  • r

r e m

  • t

e u s e ( r e m

  • t

e a c c e s s p r

  • t
  • c
  • l

)

PREFIX abc: <http://mynamespace.com/exampleOntology#> SELECT ?capital ?country WHERE { ?x abc:cityname ?capital. ?y abc:countryname ?country. ?x abc:isCapitalOf ?y. ?y abc:isInContinent abc:africa. }

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SLIDE 63

OWL (Web Ontology Language)

  • O

WL a d d s e x p r e s s i v i t y t

  • R

D F S c h e m a t

  • e

n a b l e m

  • r

e p

  • w

e r f u l s e m a n t i c s :

c a r d i n a l i t y r e s t r i c t i

  • n

s ,

l

  • c

a l r a n g e c

  • n

s t r a i n t s ,

e q u a l i t y

  • f

r e s

  • u

r c e s ,

i n v e r s e , s y m m e t r i c a n d t r a n s i t i v e p r

  • p

e r t i e s ,

b

  • l

e a n c l a s s c

  • m

b i n a t i

  • n

s ,

d i s j

  • i

n t n e s s a n d c

  • m

p l e t e n e s s , …

  • O

WL L i t e : s u b s e t

  • f

f e a t u r e s t h a t i s e a s y t

  • i

m p l e m e n t a n d u s e

  • O

WL D L : s u b s e t

  • f

f e a t u r e s s u p p

  • r

t i n g d e s c r i p t i

  • n
  • l
  • g

i c r e a s

  • n

i n g ( e . g . u s e f u l f

  • r
  • n

t

  • l
  • g

y c

  • n

s t r u c t i

  • n

)