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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
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Semantic Networks

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Artificial Intelligence

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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

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