Patent ID: 8521523

Claim:
A computer-implemented method comprising: Selecting, by one or more computers, a target out of vocabulary rate that indicates a rate at which a word included in a search query is not included in a vocabulary; selecting, by one or more computers, a target percentage of user sessions, wherein the target percentage represents a percentage of user sessions that include search queries that include words that are included in a vocabulary of words at a rate that satisfies the target out of vocabulary rate; obtaining, by one or more computers, a training set of user sessions, each user session in the training set comprising one or more search queries that each include one or more words; and determining, by one or more computers, and based on the training set, a minimum training data freshness for a vocabulary of words, the minimum training data freshness corresponding to at least the target percentage of the user sessions in the training set experiencing the target out of vocabulary rate.