title: NLP POS Tree understanding
body: <p>How does tree gets formed in NLP -> parts of speech tagging. What is algorithm behind this? 
  (S
     (NP Alice)
     (VP
        (V chased)
        (NP
           (Det the)
           (N rabbit))))</p>
  
  <p>for instance how can Det "the" and N "rabbit" become NP (grouped under NP?)
  What is algorithm behind tree formation and aggregation of nodes </p>