A computer-implemented method of determining search intent, comprises: receiving a search query; searching content across a plurality of content classes using the search query, so as to obtain a plurality of search results; deriving summary data from the search results; applying the summary data to a trained machine learning model; and determining from the machine learning model a selected one of the content classes corresponding to the search intent of the search query.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A computer-implemented method of determining search intent, comprising: a) receiving a search query at a search engine; b) searching content across a plurality of content classes using the search query, so as to obtain a plurality of search results; c) deriving, from the plurality of search results, summary data relating to the content class of the plurality of search results; d) applying the summary data to a trained machine learning model; and e) determining from the trained machine learning model a selected one of the content classes corresponding to the search intent of the search query. 2. The method of claim 1, further including outputting only the search results that belong to the selected one of the content classes. 3. The method of claim 2, including outputting only the search results belonging to the selected one of the content classes if the confidence indication exceeds a threshold, in accordance with a confidence indication of the selected one of the content classes received from the machine learning model. 4. The method of claim 2, further including formatting the output search results according to the selected one of the content classes. 5. The method of claim 4, wherein the output search results are prioritized according to the selected one of the content classes. 6. The method of claim 1, wherein the search results are formatted according to the type of a device from which the search query was received. 7. The method of claim 1, including caching the selected one of the content classes as corresponding to the search query, and retrieving the selected one of the classes from the cache if a subsequent search query corresponding to said search query is received. 8. The method of claim 1, wherein the machine learning model comprises a neural network or support vector machine. 9. The method of claim 1, further comprising: a) receiving a set of training queries, each having an associated predetermined content class corresponding to the search intent thereof; and b) training the machine learning model with the set of training queries. 10. The method of claim 9, further including: receiving a set of validation queries, each having an associated predetermined content class corresponding to the search intent thereof, and validating the machine learning model by performing the method of claim 1 for each of the validation queries, and comparing for each query the selected one of the classes as determined by the machine learning model with the predetermined content class associated with the respective query, to determine an error rate for the machine learning model. 11. The method of claim 10, comprising repeating said training and validation until the error rate falls below a threshold. 12. The method of claim 1, wherein the summary data includes a normalised number of results from each of the content classes. 13. The method of claim 1, wherein the summary data includes an indication of the content class of the most relevant one of the search results. 14. A computer program product comprising: program code means for storing program operations; a processor at a search engine that performs the stored program operations to perform a method comprising: a) receiving a search query at the search engine; b) searching content across a plurality of content classes using the search query, so as to obtain a plurality of search results; c) deriving, from the search results, summary data relating to the content class of the search results; d) applying the summary data to a trained machine learning model; and e) determining from the machine learning model a selected one of the content classes corresponding to the search intent of the search query. 15. A search server comprising: program code means for storing program operations; a processor at a search engine that performs the stored program operations to perform a method comprising: a) receiving a search query at a search engine; b) searching content across a plurality of content classes using the search query, so as to obtain a plurality of search results; c) deriving, from the search results, summary data relating to the content class of the search results; d) applying the summary data to a trained machine learning model; and e) determining from the machine learning model a selected one of the content classes corresponding to the search intent of the search query. 16. The search server of claim 15, wherein the search server comprises a vertical search server. 17. A search intent classifier comprising: a) an input terminal that receives summary data from results of a search across a plurality of content classes using a search query; b) a trained machine learning model that receives the summary data and determines therefrom a selected one of the content classes corresponding to the search intent of the search query; and c) an output module that indicates the selected one of the content classes.