BM25F

[lgrz]

Add BM25F as a feature from Microsoft Cambridge at TREC–13: Web and HARD tracks

Main points to consider (this issue should be expanded upon closer to implementation):

• Requires field support for inverted indexes
• How will the user configure the various parameters available

Useful paper resources:

• Microsoft Cambridge at TREC–13: Web and HARD tracks
• Simple BM25 extension to multiple weighted fields
• Application of Dynamic Pruning to Field-Based Retrieval Models