Wolfram Technology Guide: High-Level String Computation  previous | next 
Statistical Semantic Analysis
With its WordData capabilities, Mathematica makes immediate forms of semantic analysis possible. Here is the moving average of the number of word senses in the U.S. Declaration of Independence, with the signature block at the end visibly distinct.
In[1]:=

Click for copyable input
ListLinePlot[

 MovingAverage[

  Length[WordData[ToLowerCase[#]]] & /@ 

   Flatten[StringCases[

     ExampleData[{"Text", "DeclarationOfIndependence"}, "Words"], 

     LetterCharacter ..]], 20], Filling -> Axis, 

 PlotRange -> {0, All}, Frame -> True]
Out[1]=