s --> np, vp.               
np --> pn.                
np --> det, noun.         
pn --> [john].            
pn --> [mary].                
det --> [a].
det --> [every]. 
noun --> [woman].
noun --> [siamese,cat].  
vp --> iv.
vp --> tv, np.
iv --> [walks].
tv --> [loves].
tv --> [likes].