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