Similarity for Span and Boolean query

[J.Zhu]

Hi, all,
 
The equation for similarity is given on this web page:
http://lucene.apache.org/java/docs/api/org/apache/lucene/search/Similari
ty.html
 
I would like to know what are the equations for similarity if the query
is a span or boolean query.
 
Jianhan