BACKGROUND

This specification relates to systems receiving sequential queries during a single user session and determining query refinements based on the sequence of queries.

The Internet provides access to a wide variety of resources, for example, video files, image files, audio files, or Web pages, including content for particular subjects, book articles, or news articles. A search system can select one or more resources in response to receiving a search query. A search query is data that a user submits to a search engine to satisfy the users informational needs. The search queries are usually in the form of text, e.g., one or more query terms, and may also include transcriptions of spoken search queries. The search system selects and scores resources based on their relevance to the search query and on their importance relative to other resources to provide search results. The search results are typically ordered according to the scores and presented according to this order.

SUMMARY

This specification describes technologies relating to the generation and selection of query refinements using query data.

In general, one innovative aspect of the subject matter described in this specification can be embodied in methods that include the actions of receiving, by one or more computers, a first query comprising one or more n-grams for a user session, receiving, by the one or more computers, a second query comprising one or more n-grams for the user session, the second query being different from the first query and subsequent to the first query without an intervening query, determining an first set of query refinements for the first query, each of the query refinements in the first set of query refinements based on the first query, determining a second set of query refinements from the first set of query refinements, each query refinement in the second set of query refinements including at least one n-gram that is similar to an n-gram from the first query and at least on n-gram that is similar to an n-gram from the second query, scoring each query refinement in the second set of query refinements, selecting, based on the score, a third query, the third query selected from a group consisting of the second set of query refinements and the second query, and providing the third query as input to a search operation. Other embodiments of this aspect include corresponding systems, apparatus, and computer programs, configured to perform the actions of the methods, encoded on computer storage devices.

Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. In some implementations, a search engine accesses multiple sequential queries and determines a query refinement for a received query based on the multiple sequential queries, thereby reducing the amount of user input on a user device. In some implementations, the search engine restricts query refinements to reduce the likelihood of topic drift, thereby providing refinements that are more likely to satisfy users' informational needs. The ability to refine a query in this manner enables a user to input queries in a more fluid, conversational manner, which, in turn, results in ease of use of the search engine by the users.

The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

