Language Models Web Search and Mining ecture 12: Language Models
Language Models 1 Lecture 12: Language Models Web Search and Mining
Language Models Recap Probabilistic models Binary independence model Bayesian networks for IR Language models
Language Models 2 Recap ▪ Probabilistic models: ▪ Binary independence model ▪ Bayesian networks for IR ▪ Language models
Language Models This lecture The Language model approach to Ir Basic query generation model Alternative models
Language Models 3 This lecture ▪ The Language Model Approach to IR ▪ Basic query generation model ▪ Alternative models
Language Models Standard probabilistic ir Information need P(r O, d) d1 matching d2 query dn document collection
Language Models 4 Standard Probabilistic IR query d1 d2 dn … Information need document collection matching P(R | Q,d)
Language Models iR based on Language Model (Lm) Information …………… need P(2IM) Mdi generation d2 query a common search heuristic is to use Mdn words that you expect to find in matching documents as your query document collection The LM approach directly exploits that idea
Language Models 5 IR based on Language Model (LM) query d1 d2 dn … Information need document collection generation ( | ) P Q Md 1 Md M d2 … n M d ▪ A common search heuristic is to use words that you expect to find in matching documents as your query. ▪ The LM approach directly exploits that idea!