public class IntTaggedWord
implements java.io.Serializable, java.lang.Comparable<IntTaggedWord>
Represents a WordTag (in the sense that equality is defined
on both components), where each half is represented by an
int indexed by a Index. In this representation, -1 is
used to represent the wildcard ANY value, and -2 is used
to represent a STOP value (i.e., no more dependents).
TODO: does that cause any problems regarding unseen words also being -1?
TODO: any way to not have links to the Index in each object?