I think Lucene in Action does a good job of it. There is also a formula given in the javadoc for DefaultSimilarity http://lucene.apache.org/java/docs/api/org/apache/lucene/search/Similarity.html
See my comments below (inline) On 3/2/06, Eugene <[EMAIL PROTECTED]> wrote: > Hi All, > > I'm not sure how to interpret the result of the toString method of > Explanation. I'm trying to see the values of each component of the > Default Similarity formula for a particular query and a doc. Given > below is a sample of my Explanation output. Many thanks if anyone could > help explain some of the values or direct me to a place that does so. > > Explanation = 0.683103 = product of: > 1.7077575 = sum of: > 0.184242 = weight(Contents:x in 78), product of: > 0.13565542 = queryWeight(Contents:x), product of: the queryWeight is query-specific... it will have the same value for all documents matching the query. > 2.509232 = idf(docFreq=85) inverse document frequency... term "x" appears in 85 documents. > 0.054062527 = queryNorm queryNorm is a normalization factor... 1/sqrt(sum of all query weights squared) If you had a boost, it would also be multiplied into the queryWeight at this point. > 1.3581617 = fieldWeight(Contents:x in 78), product of: fieldWeight components are document specific. > 1.7320508 = tf(termFreq(Contents:x)=3) "x" appears 3 times in the field for this document > 2.509232 = idf(docFreq=85) same as the previous idf factor - 85 documents contain "x" > 0.3125 = fieldNorm(field=Contents, doc=78) the norm is calculated at index time... it's the length normalization factor (1/sqrt(num tokens in this field)) multipled by any on the field or document. > 0.184242 = weight(Contents:x in 78), product of: > 0.13565542 = queryWeight(Contents:x), product of: > 2.509232 = idf(docFreq=85) > 0.054062527 = queryNorm > 1.3581617 = fieldWeight(Contents:x in 78), product of: > 1.7320508 = tf(termFreq(Contents:x)=3) > 2.509232 = idf(docFreq=85) > 0.3125 = fieldNorm(field=Contents, doc=78) > 0.26218253 = weight(Contents:y in 78), product of: > 0.16182467 = queryWeight(Contents:y), product of: > 2.9932873 = idf(docFreq=52) > 0.054062527 = queryNorm > 1.6201642 = fieldWeight(Contents:y in 78), product of: > 1.7320508 = tf(termFreq(Contents:y)=3) > 2.9932873 = idf(docFreq=52) > 0.3125 = fieldNorm(field=Contents, doc=78) -Yonik --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
