1. A method for determining patterns in an input string of tokens, comprising steps of: identifying extensible patterns in the input string; creating an inexact tree for the input string, using the patterns identified; and displaying a set of extensible patterns identified by the inexact tree; wherein creating the inexact tree comprises creating nodes and edges, connecting the nodes, wherein each node represents a subset of a string and each edge connects a lower order node to a higher order node; wherein each subset comprises a pattern comprising extensible string; and wherein each extensible string comprises at least one dot token.