Signs, Processes, and Language Games
John F. Sowa
Systems, scientific and philosophic, come and go. Each method of limited understanding is at length exhausted. In its prime each system is a triumphant success: in its decay it is an obstructive nuisance.
Alfred North Whitehead, Adventures of Ideas
Questions to Consider
- How can we build large ontologies?
- How can we accommodate existing ontologies, databases, knowledge bases, and web sites?
- How do we relate them to natural languages?
- How do we reason with them and about them?
- What foundations do we adopt?
- What structures do we build?
Large Hand-Coded Ontologies
Three large ontologies:
- Cyc: 100,000 concept types with over a million axioms.
- Electronic Dictionary Research (EDR): 400,000 concept types with mappings to English and Japanese words.
- WordNet: 166,000 English word senses with related projects for other languages.
Building these things requires a great deal of time and money.
Small Hand-Coded Ontologies
Can such simple systems coexist peacefully with the grand ontologies?
Purpose of This Talk
- Propose a more flexible structure.
- Show how it can coexist with various kinds of systems, large and small.
- Show how it can support natural language processing.
- Show how it can support detailed deductions for knowledge-based systems.
- The ultimate questions of what exists are being addressed by the natural sciences: physics, chemistry, biology, and astronomy.
- The structure and purpose of artifacts are being addressed by engineers, by artisans, and by everyone who uses them.
- The languages for talking about all these things are being studied by linguists and are being extended by people everywhere whenever they open their mouths.
- The role of the philosophers is to analyze these things and their interrelationships.
- AI researchers must apply logic, linguistics, philosophy, and computer science to the task of knowledge representation.
Foundations of Ontology
Semiotics by Charles Sanders Peirce:
- Signs of all kinds: Words, sentences, books, images, concepts, thoughts, and sensory inputs of all modalities.
- Logic and natural languages are important special cases.
Process philosophy by Alfred North Whitehead:
- The ultimate existents are processes.
- Forms are abstractions from processes that may be designated by signs.
- Objects are "permanences amidst the flux" that are characterized by "forms of definiteness."
Language games by Ludwig Wittgenstein:
- The meaning of a word is determined by its use in a language game.
- The number of possible language games is open ended.
- New language games are constantly being invented for special purposes as modifications or extensions of older games.
- Words only have a precise, formalizable meaning with respect to a particular language game.
- The same word may have different meanings in different games.
Language games for support
Consider the verb support in the following sentences:Tom supported the tomato plant with a stick.These sentences all use the verb support in the same syntactic pattern:
Tom supported his daughter with $10,000 per year.
Tom supported his father with a decisive argument.
Tom supported his partner with a bid of 3 spades.A person supported NP1 with NP2.Each use of support can only be understood with respect to a particular subject matter:
- Physical structures, financial arrangements, intellectual debate, or the game of bridge.
Different Games with the Same Pieces
Games of go and gomoku use identical pieces
Same syntax, but different scoring rules
How Language Games Work
The mapping from language to reality varies with each language game:
- Words are like playing pieces that may be used and reused in different language games.
- Associated with each word is a small number of lexical patterns that determine the rules that are common to all the language games that use the word.
- Meanings are deeper conceptual patterns that change from one language game to another.
- Metaphor and conceptual refinement are techniques for transferring the lexical patterns of a word to a new language game and thereby creating new conceptual patterns for that game.
- Words can only be formally defined (axiomatized) within a particular language game — contract bridge and auction bridge require different axioms.
Two hierarchies for each natural language:
- Words. A hierarchy of words and word senses, similar to WordNet and EDR.
- Canonical graphs. A partial ordering of conceptual graphs that express the lexical patterns associated with each word of each language.
Two language-independent hierarchies:
- Types. A lattice of all the concept and relation types that are used in the theories and in the canonical graphs.
- Theories. An open-ended, potentially infinite, lattice of all possible theories, each corresponding to a possible language game.
Every new language game makes a word more ambiguous:
- Words. As many different senses as there are language games that use them.
- Fully specified concept types. Very narrow types express a single word sense that is used in only a single language game (theory).
- Underspecified concept types. Very broad types that contain only the meaning that is common to all their subtypes.
A Narrow Type Broadens
The many subtypes of the word che
Navigating the Lattice of Theories
Example: earth and sun map to the hydrogen atom.
Belief-revision operators can accommodate such theories
- A single, consistent, all-encompassing theory is impossible, at least within the foreseeable future.
- The enormous number of special-purpose solutions aren't going to disappear overnight.
- The infinite hierarchy of theories can accommodate everything.
- Belief revision with analogy is essential to relate independently developed solutions.
Copyright ©2001, John F. Sowa