Natural Language Interface Gems

David H.D. Warren
Fernando C.N. Pereira

Chat-80

1981 - 1982, David H.D. Warren, Fernando C.N. Pereira (SRI) [source code]

This is a gem, because

Together with the system of Veronica Dahl, on which it is based, these are the first NLI systems built in Prolog. The code of Chat-80 was circulated widely, and formed the basis of several other experimental NliDbs (e.g. Masque)

Characteristics

Programming language
Prolog
Natural language
English
Type of analysis
Semantics-based
Influenced by
Veronica Dahl, LUNAR
Language constructs
Noun Phrases, Verb Phrases, Preposition Phrases, Determiner Phrases, Relative Clauses, Negations, Extraposition

Data flow

Natural Language input
Tokenize
  • Lexicon lookup
Tokens
Parse
Parser type
Top-down backtracking
Grammar type
Extraposition Grammars
    Syntactic form
    Interpret
    • Semantic attachment
    • Semantic composition
    • Quantifier scoping
    Semantic form
    (FOPC with extensions)
    • Uses constants for proper nouns
    Convert
    • Syntactic rewrites
    • Optimize query
    Knowledge source form
    • Handle aggregations
    Execute
    Knowledge Base
    A Prolog database
      Knowledge base answers
      Answer
        Natural Language output

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