Each rule has following syntax:
feature-name-pattern window condition
feature-name-pattern is a string that describes what
the generated feature name will be. Some special characters
allow the insertion of variable values in the feature name. See
section 4.4.3 for a description of the syntax of
feature name patterns.
window is a range in the format [num,num], and
states the words around the target word for which the feature has
to be computed. A window of [0,0] means that the feaure
is only checked for the target word.
condition is the condition that a word has to satisfy
in order to get the features extracted by the rule. See section
4.4.4 for a description of condition syntax.