hi-level implementation of Inverted Lists in Key-Value Stores:
(Python and MongoDB)
import re
def getwords(doc):
   splitter = re.compile('\\W*')
   #split the words by non-alpha characters
   words = [s.lower() for s in splitter.split(doc)]
   return words;

class Vocabulary:
def makeInvertedIndexSortedByKey(doc):
  i = 0;
  for w in getwords(doc):
   Position = i++
   Frequency = (doc.id, freq(w)++, offset(Position))
   PostingsList = (Field, w, freq(doc.id), offset(Frequency))
   FieldDef = (Field,  indexed=true, stored=true, offset(PostingsList))