Semantic Network

A semantic network is a graph whose nodes represent individuals and whose directed arcs represent binary relationships. (Kowalski)

Any set of variable-free binary relationships (assertions) or any set of n-ary relationships that can be converted to binary relationships can be represented graphically as a simple semantic network. All information concerning an individual in the network is accessible from its node.

Marsha

Jan

Cindy

Carol

gold

ha

ir of

hair

of

mother of

child of

mother_of(carol,marsha)

mother_of(carol,jan)

mother_of(carol,cindy)

child_of(marsha,carol)

child_of(jan,carol)

child_of(cindy,carol)

hair_of(carol,gold)

hair_of(marsha,gold)

hair_of(jan,gold)

hair_of(cindy,gold)

Binary Relationships Simple Semantic Network

Greg

Peter

Bobby

Mike

Alice

housekeeper

man

is ais a

is a

is a

boss of

emplo

y of

father of

child of

father_of(mike,greg)

father_of(mike,peter)

father_of(mike,bobby)

child_of(greg,mike)

child_of(peter,mike)

child_of(bobby,mike)

boss_of(mike,alice)

employ_of(alice,mike)

is_a(mike,man)

is_a(greg,man)

is_a(peter,man)

is_a(bobby,man)

is_a(alice,housekeeper)

Binary RelationshipsSimple Semantic Network

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

is a

boss of

emplo

y of

mother offather of

child of child of

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

married to

is a

married to

boss of

emplo

y of

mother offather of

child of child of

Merge Two Networks:

married_to(mike,carol)

married_to(carol,mike)

Extended Semantic Network

An extended semantic network has the same graphical and information storage capabilities as a simple semantic network, except that it has been extended to allow the nodes to be constants, variables, or terms constructed using function symbols. Further, the arcs of the extended semantic network can represent conditions and alternative conclusions. Extended semantic networks can be thought of as a pictorial syntax for clausal form.

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

married to

is a

married to

boss of

emplo

y of

mother offather of

child of child of

G

father of

child of

father_of(mike,G)child_of(G,carol)

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

married to

is a

married to

boss of

emplo

y of

mother offath

er

of

child of child of

father_of(mike,marsha)

father_of(mike,jan)

father_of(mike,cindy)

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

married to

is a

married to

boss of

emplo

y of

mother offather of

child of child of

G

father of child of

B

mother of

child

of

mother_of(carol,B)child_of(B,mike)

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

married to

is a

married to

boss of

emplo

y of

mo

the

r offa

the

r o

fchild of child of

father_of(mike,marsha)

father_of(mike,jan)

father_of(mike,cindy)

mother_of(carol,greg)

mother_of(carol,peter)

mother_of(carol,bobby)

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

married to

is a

married to

boss of

emplo

y of

mother offather of

child of child of

G

father of

child of

B

mother of

child

of

Representation of N-ary Relationships in Binary Form

Events which entail multiple individuals or actions are often represented by n-ary assertions. For example, the statement “Alice cooks meatloaf for the family” might be represented as follows:

cook(alice,meatloaf,family)

Unfortunately, n-ary relationships can be ambiguous. It is possible to re-express an n-ary relationship as a conjunction of n+1 binary relationships.

Alice

e1

actor

cooking

act of

meatloaf

objec

t

family

recipient

cook(alice,meatloaf,family)

becomes

act_of(e1,cooking) object(e1,meatloaf)

actor(e1,alice) recipient(e1,family)

e1 is an event, which is an act of cooking. e1 has an actor, Alice; an object, meatloaf; and a recipient of the action, family.

Alice

e1

actor

cooking

act of

meatloaf

objec

t

family

recipient

wa

nts

Carol

It is now easier to represent the relationships that other nodes may have with the event e1, such as in the case of:

Carol wants Alice to cook meatloaf for the family.

Greg

Peter

Bobby

Marsha

Jan

Cindy

Mike Carol

Alice

housekeeper

man gold

is ais a

is a

ha

ir of

hair

of

married to

is a

married to

boss of

emplo

y of

mother offather of

child of child of

G

father of

child of

B

mother of

child

of

e1w

an

ts

actor

cooking

act of

meatloaf

objec

t

family

recipient

Kowalski, Robert A. (1979) Logic for Problem Solving. North-Holland, Amsterdam etc.

Available for download at:

http://www-lp.doc.ic.ac.uk/UserPages/staff/rak/rak.html

References

is(this,the_end)