14. One or more computer-readable storage media storing computer-executable instructions that, when executed on one or more processors, cause the one or more processors to perform operations comprising: receiving an input query transmitted over a network; determining an input query pattern associated with the input query; accessing a library comprising one or more query patterns associated with one or more predefined search task categories by one or more transition probabilities, each of the one or more predefined search task categories associated with a task to be accomplished; classifying the input query pattern into one or more search tasks according to the one or more predefined search task categories, the classifying based at least in part on a lookup of the input query pattern in the library and identifying one or more tasks to be accomplished associated with the one or more predefined search task categories associated with a query pattern of the one or more query patterns similar to the input query pattern; and determining a search result based at least in part on the classified one or more search tasks, the search result based at least in part on the identified one or more tasks to be accomplished.
14. One or more computer-readable storage media storing computer-executable instructions that, when executed on one or more processors, cause the one or more processors to perform operations comprising: receiving an input query transmitted over a network; determining an input query pattern associated with the input query; accessing a library comprising one or more query patterns associated with one or more predefined search task categories by one or more transition probabilities, each of the one or more predefined search task categories associated with a task to be accomplished; classifying the input query pattern into one or more search tasks according to the one or more predefined search task categories, the classifying based at least in part on a lookup of the input query pattern in the library and identifying one or more tasks to be accomplished associated with the one or more predefined search task categories associated with a query pattern of the one or more query patterns similar to the input query pattern; and determining a search result based at least in part on the classified one or more search tasks, the search result based at least in part on the identified one or more tasks to be accomplished. 19. The one or more computer-readable storage media of claim 14 , wherein a transition probability of the one or more transition probabilities represents the probability that a random walk beginning from the query pattern associated with the transition probability will include the predefined search task category associated with the transition probability.