How to set threshold for categorized document as Matched ,Partial Match, No Match with query.

[Rajendra Rao]

Hi

We used apache lucene for ranking documents .We have documents with its
score  .Now our requirements is to set a threshold so that  we can show
that documents has matched ,no matched ,or partial match based on the
threshold .How can we set this threshold because  match score has decimal
number and it is also variable ?
 please  guide us.