Chapter 8: Syntax

Structual Ambiguity

 A situation in which a single phrase or sentence has two ( or more) different underlying structures and interpretations.

Eg: Annie pumped into a man with an umbrella

Syntactic ambiguity occurs when the grammatical arrangement of words makes the meaning of a sentence unclear. The meaning of each word may be clear, but we cannot understand the overall sense. Here are a few.

MOVEMENT' RULES

-> A syntactic rule

-> moving/ changing parts of structures to different positions 

Eg: You would help the little boy.

Would you help the little boy?

-> Aux-movement

-> A special arrow (=>) is used to indicate that a constituent can be moved.

Eg: Aux-movement : NP Aux VP=> Aux NP VP

Syntactic Analysis

Syntax analysis uses context-free grammar to define programming language syntax, with two main approaches: top-down and bottom-up parsing.

Phrase structure rules 

Phrase structure rules (or PSRs) are the rules we use to build tree diagrams. They are a way to describe and record which kind of phrases can occur inside and modify which other kinds of phrases. They are also hypotheses, so if we find a sentence that doesn’t fit with our rules, we should not panic! 

S -> NP VP

NP -> ( art (adj) N, Pro, PN)

VP -> V NP

Lexical rules

 Lexical rules: used to transform the structures generated by the phrase structure rules into proper and understandable English 

= Lexical rules: rules stating which words can be used for constituents generated by phrase structure rules.

               PN -> {John, Mary }

               N -> { girl, dog, boy }

               V -> { followed, helped, saw} 

               Art -> { a, the}

              Adj -> { big, small }

              Pro -> {it, you}

Tree diagrams

One of the best ways to create a visual representatiion od underlying syntactic structure is through tree diahgrams.  

NP -> ART N                                                    NP

                                                                      Art              N

                                                                       A                dog

                          VP

          V                               NP

                                       Art     N

   followed               the     boy

Tree diagrams of English sentences

We can now put together tree diagrams for whole sente ces, hierarchically organized, as shown in figire. Notice that essientially the same bsic tree diagram strucuture is the foundation for all the different setences.

(1)                               S                                                                             (2)                                          S

          NP                                            VP                                                                        NP                                      VP

Art        N                              V                        NP                                                       Pro                           V                   NP

                                                                     Art          N                                                                                                            Pro

A           dog                  followed       the         boy                                               You                          saw              it