We have a new tutorial on Okapi Simple BM25 with Extension to Multiple Fields.

09-29-2016 Update: Sorry! Wait for an updated version of tutorial

Unlike the BM25, this model (known as Simple BM25F) incorporates the structure of documents into the scoring process.

 

In addition, we’ve uploaded a new, improved, and expanded version of the Okapi Best Match 25 tutorial.

09-29-2016 Update:

http://www.minerazzi.com/tutorials/okapi-bm25-model.pdf

 

Have a great IR day!