Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
Semantic Networks
Definition
Semantic Net
• Form of knowledge representation
• Predicate logic alternative
• Labelled directed graph
• Components:
• No...
Semantic Nets
• isa(person, mammal)
• instance(Mike Hall, person)
• team(Mike Hall, Cardiff)
Kinds of Semantic Nets
Definitional Networks
• Emphasize the subtype or is-a
relation between a concept type
and a newly d...
Kinds of Semantic Nets
Assertional Networks
• Designed to assert propositions.
Kinds of Semantic Nets
Implicational Networks
• Uses implication as the primary
relation for connecting nodes.
Kinds of Semantic Nets
Executable Networks
• Contain mechanisms that can
cause some change to the
network itself.
Kinds of Semantic Nets
Learning Networks
• Networks that build or extend
their representations by
acquiring knowledge from...
Kinds of Semantic Nets
Hybrid Networks
• Networks that combine two or
more of the previous
techniques, either in a single
...
Semantic Relations
• Antonymy - A is the opposite of B (Cold is the opposite of warm)
• Holonymy - B has A as a part of it...
Common Semantic Relations
• There is no standard set of relations for semantic networks, but the following
relations are v...
Inheritance
• A key concept in semantic networks and can be represented naturally
by following ISA links.
• In general, if...
Common Semantic Relations
• There is no standard set of relations for semantic networks, but the following
relations are v...
Converting to Semantic Net
Example
• Bill is taller than John.
Bill John
taller_than
Bill John
value
h1 h2
greater_than
180
nodes represent object, and arcs represent
relationships between those objects
Steps
• Draw Relations on the basic of primitives
• Represent Complicated Relations with this primitives.
taller_than
h1 h...
Reification
• reify v : consider an abstract concept to be real
• Non-binary relationships can be represented by “turning ...
EXAMPLE
• Tom is a cat.
• Tom caught a bird.
• Tom is owned by John.
• Tom is ginger in colour.
• Cats like cream.
• The c...
Disadvantages of using Semantic
Nets
Disadvantages
• There is no standard definition of link names
• Semantic Nets are not intelligent, dependent on creator
• ...
Advantages of using Semantic
Nets
Advantages
• Natural
• Modular
• Efficient
• Convey meaning in a transparent manner
• Simple
• Understandable
• Translatab...
References:
• http://www.jfsowa.com/pubs/semnet.htm
Semantic Networks
Semantic Networks
Upcoming SlideShare
Loading in …5
×

Semantic Networks

14,380 views

Published on

Artificial Intelligence

Published in: Education
  • Be the first to comment

Semantic Networks

  1. 1. Semantic Networks
  2. 2. Definition
  3. 3. Semantic Net • Form of knowledge representation • Predicate logic alternative • Labelled directed graph • Components: • Nodes – object or concept • Links – relation between nodes.
  4. 4. Semantic Nets • isa(person, mammal) • instance(Mike Hall, person) • team(Mike Hall, Cardiff)
  5. 5. Kinds of Semantic Nets Definitional Networks • Emphasize the subtype or is-a relation between a concept type and a newly defined subtype.
  6. 6. Kinds of Semantic Nets Assertional Networks • Designed to assert propositions.
  7. 7. Kinds of Semantic Nets Implicational Networks • Uses implication as the primary relation for connecting nodes.
  8. 8. Kinds of Semantic Nets Executable Networks • Contain mechanisms that can cause some change to the network itself.
  9. 9. Kinds of Semantic Nets Learning Networks • Networks that build or extend their representations by acquiring knowledge from examples.
  10. 10. Kinds of Semantic Nets Hybrid Networks • Networks that combine two or more of the previous techniques, either in a single network or in separate, but closely interacting networks.
  11. 11. Semantic Relations • Antonymy - A is the opposite of B (Cold is the opposite of warm) • Holonymy - B has A as a part of itself (Bedroom has bed) • Homonymy - A and B, are expressed by the same symbol. (Both a financial institution and a edge of a river are expressed by the word bank) • Hypernymy - A is the superordinate of B. A is the general kind of B(Animal is a hypernym of dog) • Hyponymy or troponomy - A is a subordinate of B. A is a specific kind or instance of B (Dog is a hyponym of animal) • Meronymy - A is part of B (Engine is part of car) • Synonymy - A denotes the same as B (Happy is synonym of blissful)
  12. 12. Common Semantic Relations • There is no standard set of relations for semantic networks, but the following relations are very common: • INSTANCE: X is an INSTANCE of Y if X is a specific example of the general concept Y. • Example: Elvis is an INSTANCE of Human • ISA: X ISA Y if X is a subset of the more general concept Y. • Example: sparrow ISA bird • HASPART: X HASPART Y if the concept Y is a part of the concept X. (Or this can be any other property) • Example: sparrow HASPART tail
  13. 13. Inheritance • A key concept in semantic networks and can be represented naturally by following ISA links. • In general, if concept X has property P, then all concepts that are a subset of X should also have property P.
  14. 14. Common Semantic Relations • There is no standard set of relations for semantic networks, but the following relations are very common: • INSTANCE: X is an INSTANCE of Y if X is a specific example of the general concept Y. • Example: Elvis is an INSTANCE of Human • ISA: X ISA Y if X is a subset of the more general concept Y. • Example: sparrow ISA bird • HASPART: X HASPART Y if the concept Y is a part of the concept X. (Or this can be any other property) • Example: sparrow HASPART tail
  15. 15. Converting to Semantic Net
  16. 16. Example • Bill is taller than John. Bill John taller_than Bill John value h1 h2 greater_than 180
  17. 17. nodes represent object, and arcs represent relationships between those objects
  18. 18. Steps • Draw Relations on the basic of primitives • Represent Complicated Relations with this primitives. taller_than h1 h2 greater_than
  19. 19. Reification • reify v : consider an abstract concept to be real • Non-binary relationships can be represented by “turning the relationship into an object” • Example: a giver, a recipient and an object, give(john,mary,book32) give john book32 mary recipient giver object
  20. 20. EXAMPLE • Tom is a cat. • Tom caught a bird. • Tom is owned by John. • Tom is ginger in colour. • Cats like cream. • The cat sat on the mat. • A cat is a mammal. • A bird is an animal. • All mammals are animals. • Mammals have fur.
  21. 21. Disadvantages of using Semantic Nets
  22. 22. Disadvantages • There is no standard definition of link names • Semantic Nets are not intelligent, dependent on creator • Links are not all alike in function or form, confusion in links that asserts relationships and structural links. • Undistinguished nodes that represent classes and that represent individual objects. • Links on objects represent only binary relations. • Negation, disjunction and general non-taxonomic knowledge are not easily expressed.
  23. 23. Advantages of using Semantic Nets
  24. 24. Advantages • Natural • Modular • Efficient • Convey meaning in a transparent manner • Simple • Understandable • Translatable to PROLOG w/o difficulty
  25. 25. References: • http://www.jfsowa.com/pubs/semnet.htm

×