Introduction to semantic networks and conceptual graphs Based upon a lecture from Bertil Ekdahl respeo@telia.com
Some useful links Logic notions and basic articles: http://xml.coverpages.org/ni2002-04-08-a.html The DARPA Agent Markup Language: http://www.daml.org/ The OWL language: http://www.w3.org/tr/owl-features/ 2
Language Meaning is created in our brain, based upon our sensations. That is why one may create a mocking world, good or bad. There is no point in having a well developed mechanism for conceptualising the sensations, if we were not capable of communicating these concepts. Here language comes into play. Language allows us to communicate ideas, which implies the possibility of having a social meaning. Without language, we each live in our own separate mental world. With language, we can share the world inhabited by others. With a language it is possible to influence the mind of another individual. 3
From subjectivity to objectivity Language bear our cognitively created concepts. How is it possible that subjective meanings then become objective facilities? The same question is raised by Gärdenfors: But, if everybody can mandate his own cognitive meaning, how can we then talk about the meaning of an expression? And how can somebody be wrong about the meaning? Gärdenfors claims that the meanings are individually constructed but the social meaning of a sentence is not determined by the mental conceptual structure of a single individual. Instead the jointly (social) meaning, together with a semantic power structure, determines the social meaning. 4
Semantics The meaning of a word, phrase, sentence, or text. Example: Susan saw the man in the park with a dog. Susan saw the man in the park with a statue. Susan saw the man in the park with a telescope We must have a notation where these differences can be described. 5
Semantics The meaning of a word, phrase, sentence, or text. Example: Susan saw the man in the park with a dog. Susan saw the man in the park with a statue. Susan saw the man in the park with a telescope We must have a notation where these differences can be described. 5
Semantics The meaning of a word, phrase, sentence, or text. Example: Susan saw the man in the park with a dog. Susan saw the man in the park with a statue. Susan saw the man in the park with a telescope We must have a notation where these differences can be described. 5
Semantics The meaning of a word, phrase, sentence, or text. Example: Susan saw the man in the park with a dog. Susan saw the man in the park with a statue. Susan saw the man in the park with a telescope We must have a notation where these differences can be described. 5
Semantic Net is used as a knowledge representation is a directed graph consisting of nodes, representing concepts, and edges, representing relations between concepts. 6
What is a concept? An Idea, especially an abstract idea Philosophy: A general idea or notion that corresponds to some class or entities and that consists of the characteristic or essential features of the class. From Latin conceptum something received or conceived. 7
Cat has Spine Fur has isa has Animal isa Mammal isa Bear isa isa Whale Fish lives in Water lives in
A is part of B (Meronymy) Examples. Blue is a Color Doctor is a Professional St Paul s Cathedral is a Church of England Mammal is an animal
B has A as part of itself (Holonymy) Examples. Tree has bark Tree has trunk Tree has limb Mammal has vertebra
A is a kind of B (Hyponymy) Example. Scarlet, vermilion, carmine all is a kind of red Not: Pine is a kind of tree. Pine is a tree!
A is a kind of B (Hyponymy) Example. Scarlet, vermilion, carmine all is a kind of red Not: Pine is a kind of tree. Pine is a tree! Red
A is a kind of B (Hyponymy) Example. Scarlet, vermilion, carmine all is a kind of red Not: Pine is a kind of tree. Pine is a tree! Red Tree Pine Birch
Membership isa is part of Subset Properties of members and sets.
A is superordinate of B (Hypernymy) The opposite of is a kind of. Example. Transportation includes/comprises train, airplane, automobile.
Synonym: has the same meaning. Examples of synonyms. Cat and feline. Baby and infant Smart and intelligent.
Antonyms: opposite in meaning. Examples. Up and down. Hot and cold.
Mammal isa Person has Head instance of Trombone Plays Bertil Ekdahl Orchestra HBB
Mammal isa These relations are not interesting! Person has Head instance of Trombone Plays Bertil Ekdahl Orchestra HBB
Fly Bird action (can) has Wings instance Ostrich action (can) Run
This relation means most Fly Bird action (can) has Wings instance Ostrich action (can) Run
Mammal blood temp Warm kind of Elephant color Grey isa Robin favorite food Cookies
kind of Mammal blood temp Strange modelling! Warm Elephant color Grey isa Robin favorite food Cookies
Common types of semantic nets Existential graphs (Charles S. Peirce) Conceptual graphs (John F. Sowa) Formal Concept Analysis (Rudolf Wille)
Conceptual graphs (CGs) are a system of logic based on the existential graphs of C. S. Peirce and the semantic networks of artificial intelligence. They express meaning in a form that is logically precise, humanly readable, and computationally tractable. With a direct mapping to language, conceptual graphs serve as an intermediate language for translating computer-oriented formalisms to and from natural languages. ( http://www.jfsowa.com/cg/ )
CG: John is going to Boston by bus.
As a mnemonic aid, an arrow pointing toward the circle may be read "has a(n)"; an arrow pointing away may be read "which is a(n)"; and any abbreviations may be expanded to the full forms. Go has an agent which is a person John. Go has a destination which is a city Boston. Go has an instrument which is a bus.
has which is CG for the sentence: Conceptual graphs. A conceptual graph is a graph or network of two kinds of nodes: Concepts and Relations. The nodes have arcs between them. The arcs are always directed, i.e., they have a direction. This is indicated by an arrow head.
Concepts Relations Person: Alfred Drive which is has Agent Car: Afred s car Thme
Concepts Relations Person: Alfred Drive which is has Agent Car: Afred s car Thme Alfred is driving Alfred's car
Example: Bird which is Agent has Sing A bird sing. Bird is an agent of Sing. Sing has an agent which is a bird
Nested graphs Person: Bertil Expr Believe Thme Proposition: Sun # Agnt Shine Bertil believes that the sun is shining.
John gave Mary flowers. Person: John Agnt Flower:{*} Thme Give Rcpt Person: Mary
John gave Mary flowers. But what about time? Person: John Agnt Flower:{*} Thme Give Rcpt Person: Mary
John gave Mary flowers. But what about time? Person: John Agnt Flower:{*} Thme Give Rcpt Time: past When Person: Mary
Online Course in Knowledge Representation using Conceptual Graphs Aalborg University http://www.huminf.aau.dk/cg/
End For this time