The Chomsky Hierarchy

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# The Chomsky Hierarchy - PowerPoint PPT Presentation

The Chomsky Hierarchy. Significance of the grammar classification The Chomsky Hierarchy of Grammars Using the Chomsky Hierarchy in Proofs Context Sensitive Grammar Construction. Significance of the grammar classification. Each of the four grammar classes has a simple yet powerful automaton.

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### The Chomsky Hierarchy

Significance of the grammar classification

The Chomsky Hierarchy of Grammars

Using the Chomsky Hierarchy in Proofs

Context Sensitive Grammar Construction

Significance of the grammar classification
• Each of the four grammar classes has a simple yet powerful automaton.
• A useful connection between grammars, automata, and languages.
• Simple class of automaton for simple class of grammar.
The Chomsky Hierarchy of Grammars
• Languages: r.e., CSL, CFL, RL
• Grammars: Chomsky Hierarchy -- 0, 1, 2, 3
• Automata: TM, LBA, PDA, FA
• To prove a language is to be in certain language class, you may show the language can be generated from associated grammar class. For example, G = 2 => L = CFL,

G = 0 => A = TM

Context Sensitive Grammar Construction
• CSL -- Context Sensitive Grammar, none of the examples is easy.
• The next fifty years will see natural language processing as a dominant issue -- one of research areas of Artificial Intelligence.