Lect. 11Phrase structure rules Learning objectives: To define phrase structure rules To learn the forms of phrase structure rules To compose new sentences using phrase structure rules Learning objectives: To define phrase structure rules To learn the forms of phrase structure rules To compose new sentences using phrase structure rules

Phrase structure rules are a type of rewrite rule used to describe a given language's syntax and are closely associated with the early stages ofrewrite rulesyntax Phrase structure rules are a type of rewrite rule used to describe a given language's syntax and are closely associated with the early stages ofrewrite rulesyntax

transformational grammartransformational grammar, being first proposed by Noam Chomsky in 1957.Noam Chomsky transformational grammartransformational grammar, being first proposed by Noam Chomsky in 1957.Noam Chomsky

Rewrite rules, phrase structure rules, takes the form A → X, where A is a syntactic category label, such as noun phrase or sentence, and X is a sequence of such labels and/or morphemes,.phrase structure rules syntactic categorynoun phrasesentencemorphemes Rewrite rules, phrase structure rules, takes the form A → X, where A is a syntactic category label, such as noun phrase or sentence, and X is a sequence of such labels and/or morphemes,.phrase structure rules syntactic categorynoun phrasesentencemorphemes

expressing the fact that A can be replaced by X in generating the constituent structure of a sentence.For example, the rule S → NP VP means that a sentence can

consist of a noun phrase followed by a verb phrase; further rules will specify what sub-constituents a noun phrase and a verb phrase can consist of, and so on.verb phrase consist of a noun phrase followed by a verb phrase; further rules will specify what sub-constituents a noun phrase and a verb phrase can consist of, and so on.verb phrase

Activity 1 Give examples of: Noun phrases Verb phrases 1. 2.

They are used to break down a natural language sentence into its constituent parts, also known as syntactic categories, including both lexical categories (parts of speech) and phrasal categorieslanguagesyntactic categoriesparts of speechphrasal They are used to break down a natural language sentence into its constituent parts, also known as syntactic categories, including both lexical categories (parts of speech) and phrasal categorieslanguagesyntactic categoriesparts of speechphrasal

A grammar that uses phrase structure rules is a type of phrase structure grammar. Phrase structure rules as they are commonly employed operate according to the constituency relation, and a grammar that employs phrase structure rules is therefore a constituency grammar; as such, it stands in contrast to dependency grammarsphrase structure grammarconstituencydependency grammars A grammar that uses phrase structure rules is a type of phrase structure grammar. Phrase structure rules as they are commonly employed operate according to the constituency relation, and a grammar that employs phrase structure rules is therefore a constituency grammar; as such, it stands in contrast to dependency grammarsphrase structure grammarconstituencydependency grammars

Activity 2 What phrase structure grammarWhat phrase structure grammar is?. What constituency grammar is?

Examples Phrase structure rules usually take the following form: meaning that the constituent is separated into the two sub- constituents B and C.constituent Phrase structure rules usually take the following form: meaning that the constituent is separated into the two sub- constituents B and C.constituent

: Examples for English

The first rule : An S (sentence) consists of an NP (noun phrase) followed by a VP (verb phrase).sentencenoun phraseverb phrase The second rule reads: A noun phrase consists of an optional Det (determiner) followed by an N (noun).determiner The first rule : An S (sentence) consists of an NP (noun phrase) followed by a VP (verb phrase).sentencenoun phraseverb phrase The second rule reads: A noun phrase consists of an optional Det (determiner) followed by an N (noun).determiner

The third rule means that an N (noun) can be preceded by an optional AP (adjective phrase) and followed by an optional PP (prepositional phrase). The round brackets indicate optional constituents.adjective phraseprepositional phrase The third rule means that an N (noun) can be preceded by an optional AP (adjective phrase) and followed by an optional PP (prepositional phrase). The round brackets indicate optional constituents.adjective phraseprepositional phrase

Beginning with the sentence symbol S, and applying the phrase structure rules successively, finally applying replacement rules to substitute actual words for the abstract symbols, it is possible to generate many proper sentences of English

If the rules are correct, then any sentence produced in this way ought to be grammatically (syntactically) correct.correct If the rules are correct, then any sentence produced in this way ought to be grammatically (syntactically) correct.correct

Activity3 Give examples of grammatically correct sentences:

It is also to be expected that the rules will generate syntactically correct but semantically nonsensical sentences, such as the following well-known example semantically It is also to be expected that the rules will generate syntactically correct but semantically nonsensical sentences, such as the following well-known example semantically

Examples 1.The red mouse chased the cat. 2.The black tree smiles at me 1.The red mouse chased the cat. 2.The black tree smiles at me

Colorless green ideas sleep furiously This sentence was constructed by Noam Chomsky as an illustration that phrase structure rules are capable of generating syntactically correct but semantically incorrect sentences. Noam Chomsky Colorless green ideas sleep furiously This sentence was constructed by Noam Chomsky as an illustration that phrase structure rules are capable of generating syntactically correct but semantically incorrect sentences. Noam Chomsky

Activity 4 Give examples of syntactically correct but semantically incorrect sentences

Phrase structure rules break sentences down into their constituent parts. These constituents are often represented as tree structures. The tree for Chomsky's sentence can be:tree structures Phrase structure rules break sentences down into their constituent parts. These constituents are often represented as tree structures. The tree for Chomsky's sentence can be:tree structures

The Tree for Chomsky's Sentence

Draw a tree diagram for the following 1.The old man walked slowly.

A constituent is any word or combination of words that is dominated by a single node. Thus each individual word is a constituent.

Further, the subject NP Colorless green ideas, the minor NP green ideas, and the VP sleep furiously are constituents. Phrase structure rules and the tree structures that are associated with them are a form of immediate constituents analysisimmediate Further, the subject NP Colorless green ideas, the minor NP green ideas, and the VP sleep furiously are constituents. Phrase structure rules and the tree structures that are associated with them are a form of immediate constituents analysisimmediate

An important aspect of phrase structure rules is that they view sentence structure from the top down. The category on the left of the arrow is a greater constituent and the immediate constituents to the right of the arrow are lesser constituents.

Constituents are successively broken down into their parts as one moves down a list of phrase structure rules for a given sentence Next class the on tree diagramming. The end Constituents are successively broken down into their parts as one moves down a list of phrase structure rules for a given sentence Next class the on tree diagramming. The end