week2 intro knowledge representation
TRANSCRIPT
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7/24/2019 Week2 Intro Knowledge Representation
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
Lectures on Artificial Intelligence CS364Lectures on Artificial Intelligence CS364
Introduction toIntroduction to Knowledge RepresentationKnowledge Representation
13thSeptember 2!
Dr Bogdan L. rusias!."rusias#surre$.ac.u%
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7/24/2019 Week2 Intro Knowledge Representation
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13th "o dan #$ %r&sias ' 2
Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
ContentsContents
( )efining Knowledge Representation
( Knowledge Representation Schemes
( Semantic *etwor+s
( ,a-onom.( /ntolog.
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Knowledge RepresentationKnowledge Representation
Knowledge RepresentationKnowledge Representation
( 0A representationis a set of conentions abo&t how to
describe a class of things$ A description ma+es &se of the
conentions of a representation to describe some partic&lar
thing$0 inston 12516$
( 07ood representations ma+e important ob8ects and relations
e-plicit9 e-pose nat&ral constraints9 and bring ob8ects and
relations together0 ibid5 4!
( ,he representation principle5
/nce a problem is described &sing an appropriate representation9
the problem is almost soled$
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
Starting wit& an '(a)pleStarting wit& an '(a)ple
( ,he :armer9 ,he :o-9 ,he 7oose and ,he 7rain5
,he farmer m&st get a fo-9 a goose and a sac+ of grain across a
rier9 howeer his boat is small and he can onl. carr. one thing at
a time$ ;is problem is that if he leaes the fo- with the goose the
goose will be eaten9 and if he leaes the goose with the grain9 thegrain will be eaten
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
7rain
:o-
:armer
7oose
:armer
7oose
7rain
:o-
:armer
:o-7oose
7rain
:o-
7rain
:armer
7oose
:armer
:o-7rain
7oose
7oose
:armer
:o-
7rain
:armer
7oose
:o-
7rain
:armer
7oose
:o-
7rain
:o-
:armer
7oose
7rain
:armer
:o-
7oose
7rain
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
Knowledge Representation Sc&e)esKnowledge Representation Sc&e)es
( A n&mber of +nowledge representation schemes or formalisms hae
been &sed to represent the +nowledge of h&mans in a s.stematic
manner$ ,his +nowledge is represented in a %nowledge !ases&ch that
it can be retrieed for soling problems$ Amongst the well?established
+nowledge representation schemes are5
=rod&ction R&les
Semantic *etwor+s
:rames
Concept&al )ependenc. 7rammar
Concept&al 7raphs
/ntolog.
=redicate and @odal #ogic
Concept&al or ,erminological #ogics
@# B R):
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Knowledge RepresentationKnowledge Representation
Se)antic *etwor%sSe)antic *etwor%s
( Ross D&illian 166 and 16E was among the earl. AI
wor+ers to deelop a comp&tational model which
represented 0concepts0 as &ierarc&icalnetwor+s$
( ,his model was amended with some additional
ps.chological ass&mptions to characterise the str&ct&re of
Fh&manG semantic memor.$
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
Se)antic *etwor%sSe)antic *etwor%s
( Collins and D&illian 16 proposed that5
Concepts can be represented as hierarchies of inter?
connected concept nodes e$g$ animal9 bird9 canar.
An. concept has a n&mber of associated attrib&tes at a gien leel
e$g$ animal ??H has s+in eats etc$
Some concept nodes are superordinatesof other nodes e$g$animal H bird and some are su!ordinatescanar. J bird
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Knowledge RepresentationKnowledge Representation
Se)antic *etwor%sSe)antic *etwor%s
( :or reasons of cogniti"e econo)$9 s&bordinates in&erit
all the attrib&tes of their s&perordinate concepts$
( Some instances of a concept are e(ceptedfrom the
attrib&tes that help Fh&mansG to define the s&perordinates
e$g$ ostrich is e-cepted from fl.ing
( %ario&s Fps.chologicalG processes searc&these hierarchies
for information abo&t the concepts represented$
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Knowledge RepresentationKnowledge Representation
Se)antic *etwor% '(a)pleSe)antic *etwor% '(a)ple
birdcan fl.9 &as wings9
&as feathers
salmonlayseggsswims&pstream9
ispin+9 isedible
ostrichrunsfast9 cannotfly9
istall
canar.can sing9 is.ellow
fishcan swim9 &as fins9 &as gills
ani)alcanbreathe9 caneat9
&as s+in
is+a
is+a
is+a
is+a
is+a
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
Se)antic *etwor% '(a)pleSe)antic *etwor% '(a)ple
( :rom the aboe ta-onomic organisation of +nowledge abo&t a n&mber
of different animals9 one can concl&de9 b. 0in&eriting properties
down t&e ta(ono)$09 that canaries9 ostriches and salmon all hae s+in
and can breathe$
( "&t we as h&mans can also ma+e e(ceptionsto inherited properties in
that we can represent an not?fl.ing bird in a s&b? hierarch. of birds
b. simpl. noting the e-ception9 can't fly$
( Collins and D&illian carried o&t a n&mber of tests on h&man s&b8ectsand fo&nd that the s&b8ects recognise propositions lower down the
hierarch. canar. is a .ellow bird more readil. than propositions
higher &p the hierarch. canar. has s+in$
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Knowledge RepresentationKnowledge Representation
Defining In&eritanceDefining In&eritance
( AI researchers hae refined the notion of inheritance5
It is called a specialised inferencing techni&e 0for representing
properties of classes9 e-ceptions to inherited properties9 m<iple
s&perclasses9 and str&ct&red concepts with specific relationsamong the str&ct&ral elements0 ,o&retL+. 1256$
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
Se)antic *etwor%sSe)antic *etwor%s
( A semantic networ+ is a str&ct&re for representing +nowledge as a
pattern of interconnected nodesand arcs$ *odes in the net represent
conceptsof entities9 attrib&tes9 eents9 al&es$ Arcs in the networ+
represent relations&ipsthat hold between the concepts$
( A semantic networ+ is a graph theoretic data str&ct&re whose nodes
represent word senses and whose arcs e-press se)antic relations&ips
between these word senses$
( D&illian gae an acco&nt9 perhaps first &sed b. a comp&ter scientist9 ofthe associate feat&res of h&man memor. that incorporated a spreading
actiation model of comp&tation$
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Knowledge RepresentationKnowledge Representation
*etwor%s and ,-eaning, Representation*etwor%s and ,-eaning, Representation
( ,he bios.stematic notions of ta(ono)ies9 where the
concept of s&perordinates and s&bordinates pla.s a ma8or
role on the +nowledge representation literat&re$
( ,A/*/@M /: #I:N5 ,he ta-onomic organisation of
species in a hierarchical str&ct&re5 Kingdom H =h.l&m diision in botan. H Class H /rder H :amil.
H 7en&s H Species
( Carol&s #innea&s c$1Eth cent&r. Swedish botanist
deised the s.stem of binomial nomenclat&re &sed fornaming species5
each species has a two?part #atin name9 formed b. appending a
specific epithet to the gen&s name$
,he latter is capitalised and both parts italicised$
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Artificial Intelligence CS364Artificial Intelligence CS364
Knowledge RepresentationKnowledge Representation
D/ S0/AR-A1L'
BR'AD-0LD
I*2'S2I*ALBAC2'RI0-
1*D AL/A'
KI*/D- Animaliaanimals
=lantae plants :&ngi f&ngi =ro+ar.otaebacteria
=rotoctista algae9protoLoa9 slimmo&lds
1L0- Chordata @agnolioph.ta O.gom.cota /mnibacteria Chloroph.ta
CLASS @ammalia Rosidae O.gom.cetes Nnterobacteria N&con8&gatae
RD'R Carniora Sapindales @acorales N&bacteriales O.gnematales
5A-IL Canidae Aceraceae @&coraceae E. colidoes not&a"e a fa)il$
classification7
O.gnemataceae
/'*0S Canis Acer Rhizopus Escherichia Spirogyra
S1'CI'S C. familiaris A.saccharum R. stolonifer E. Coli S. crassa
-odern 2a(ono)$ '(a)ple-odern 2a(ono)$ '(a)ple
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Knowledge RepresentationKnowledge Representation
Representation and Bios$ste)aticsRepresentation and Bios$ste)atics
( or+ in +nowledge representation has been infl&enced b.
+e. notions in bios.stematics$
( ;oweer9 there are cr&cial differences between what a
ta-onomist does and a +nowledge engineer does$
( ,he +e. difference is that of the intended a&dience in the
two cases5
for the ta-onomist the a&dience is intelligent and h&man
and for the +nowledge engineer the primar. 0a&dience0 is a
comp&ter s.stem9 or more acc&ratel. the representation program$
A ifi i l lli CS364
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Knowledge RepresentationKnowledge Representation
ntolog$ntolog$
( )efinition5
P,he science or st&d. of being that department of metaph.sics
which relates to the being or essence of things9 or to being in the
abstract$Q /N) online9 http5BBwww$oed$comB
ifi i l lliA ifi i l I lli CS364
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Knowledge RepresentationKnowledge Representation
ntolog$ntolog$
( AI e-perts9 li+e ,om 7r&ber9 s&ggest that5
0In the conte-t of +nowledge sharing9 I &se the term ontolog. to
mean aspecification of a conceptualization$ ,hat is9 an ontolog. is
a description li+e a formal specification of a program of the
concepts and relationships that can e-ist for an agent or a
comm&nit. of agents$ ,his definition is consistent with the &sage
of ontolog. as set?of?concept?definitions9 b&t more general$ And it
is certainl. a different sense of the word than its &se in
philosoph.$0 Cited from www?+sl$stanford$ed&B+stBwhat?is?an?
ontolog.$html site isited 12BB!
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Knowledge RepresentationKnowledge Representation
ntolog$ntolog$
( Also ,om 7r&ber9 s&ggest that5
0An ontolog. is an e-plicit specification of a concept&aliLation$ ,he term
is borrowed from philosoph.9 where an /ntolog. is a s.stematic acco&nt
of N-istence$ :or AI s.stems9 what e-ists is that which can be
represented$ hen the +nowledge of a domain is represented in a
declaratie formalism9 the set of ob8ects that can be represented is calledthe uni"erse of discourse$ ,his set of ob8ects9 and the describable
relationships among them9 are reflected in the representational ocab&lar.
with which a +nowledge?based program represents +nowledge$ ,h&s9 in
the conte-t of AI9 we can describe the ontolog. of a program b. defining
a set of representational terms$ In s&ch an ontolog.9 definitions associate
the names of entities in the &nierse of disco&rse e$g$9 classes9 relations9f&nctions9 or other ob8ects with h&man?readable te-t describing what the
names mean9 and formal a-ioms that constrain the interpretation and well?
formed &se of these terms$ :ormall.9 an ontolog. is the statement of a
logical theor.$0 Cited from www?+sl$stanford$ed&B+stBwhat?is?an?
ontolog.$html site isited 12BB!
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Knowledge RepresentationKnowledge Representation
ntolog$ as a Specification -ec&anis)ntolog$ as a Specification -ec&anis)
( A bod. of formall. represented +nowledge is based on a
conceptuali8ation5 the ob8ects9 concepts9 and other entities
that are ass&med to e-ist in some area of interest and the
relationships that hold among them 7enesereth T
*ilsson9 1E$( A concept&aliLation is an abstract9 simplified iew of the
world that we wish to represent for some p&rpose$
( Ner. +nowledge base9 +nowledge?based s.stem9 or
+nowledge?leel agent is committed to someconcept&aliLation9 e-plicitl. or implicitl.$
A tifi i l I t lli CS364A tifi i l I t lli CS364
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Knowledge RepresentationKnowledge Representation
ntolog$ntolog$
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ClosingClosing
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