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 L01 CFG: English CF Grammar rules


   CONTEXT-FREE GRAMMAR FOR ENGLISH

o  WRITING A TOY ENGLISH GRAMMAR: 
    Context free grammar or (a restricted) phrase structure grammar

+ An example grammar given below. The first rule says that a sentence
  (S) consists of a noun-phrase (NP) and a verb phrase (VP):

-  S   ->  NP  VP
-  NP  ->  det  adj*  n
-  NP  ->  n-proper
-  VP  ->  v  [NP]  [NP]  PP*
-  PP  ->  prep  NP

where:
+ NP: noun phrase        (Ex. the red block, a sharp arrow)
+ VP: verb phrase        (Ex. lifted the red block, fired an arrow)
+ PP: preposition phrase (Ex. with hands, at the deer)
 
-   n: noun              (Ex. boy, child, arrow, block)
- n-proper: proper noun  (Ex. Ram, Mohan)
-   v: verb              (Ex. lift, fire, give)
- det: determiner        (Ex. a, the)
- adj: adjective         (Ex. big, red, sharp)


o  EXAMPLE PHRASE STRUCTURE TREE:

The boy fired the arrow.
  
           S               
           |               
     .----------.          
     |          |          
    NP         VP          
     |          |          
   .---.    .-------.      
   |   |    |       |      
  det  n    v      NP      
   |   |    |    .----.    
  The boy fired  |    |    
                det   n    
                 |    |    
                The arrow  
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