Language Models Unigram and higher-order models ○0●● P()P(o|P(●oP(。l●o刂 Unigram Language models Easy P()P(o)P(●)P( Effective Bigram( generally n-gram) Language models P(°)P(ol●)P(olo)P(●●) Other Language models Grammar-based models(PCFGs),etc Probably not the first thing to try in irLanguage Models 10 Unigram and higher-order models ▪ Unigram Language Models ▪ Bigram (generally, n-gram) Language Models ▪ Other Language Models ▪ Grammar-based models (PCFGs), etc. ▪ Probably not the first thing to try in IR = P ( ) P ( | ) P ( | ) P ( | ) P ( ) P ( ) P ( ) P ( ) P ( ) P ( ) P ( | ) P ( | ) P ( | ) Easy. Effective!