There are index time boosts ie calculated at index time and search time boosts. The field f always relates to the field(s) that the term t appears in. My understanding is that-- Norm(t,d) includes the index time boosts for each field but I think t is only included in this calc in terms of field.getboost() -- because you effectively get the product over each field in which the specific term occurs. But you don't have s norm value for e every term- field - doc combo. Similarity (defaultsimilarity by default!) method computeNorm is used to compute this factor at indexing time so have a look at that code to see what I mean! IndexReader.norms(fieldname) gives a norm array the size of the number of docs so norm[docid] is actually used to get the index time boost for the given field/doc in which the term occurs. t.getboost() is the search time boost for the particular term -- practically this is the query boost for the term (or I think product of query boosts if the term is also a sub- query (where the surrounding query has a query boost too). I may be wrong but when I dug into the docs + code these were my conclusions! bec :) Sent from my iPhone On 02/06/2010, at 3:19 PM, Li Li wrote: > in javadoc http://lucene.apache.org/java/2_4_0/api/org/apache/lucene/search/Similarity.html#formula_norm > norm(t,d) = doc.getBoost() · lengthNorm(field) · ∏ > f.getBoost() > field > f in d named as t > whre is field come from in lengthNorm(field)? > In my option, term t may appear in a doc d many times with different > fields. So > ∏ f.getBoost() > field f in d named as t > makes sense. > But Why there is only one lengthNorm(field) ? > does it mean that norm(t,d)=norm(t.text, t.field, d)? That's is-- > every doc,every field,every term , there is a norm value ? > > --------------------------------------------------------------------- > To unsubscribe, e-mail: java-user-unsubscribe@lucene.apache.org > For additional commands, e-mail: java-user-help@lucene.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscribe@lucene.apache.org For additional commands, e-mail: java-user-help@lucene.apache.org