56. A system comprising: a memory comprising instructions executable by one or more processors; and one or more processors coupled to the memory and operable to execute the instructions, the one or more processors being operable when executing the instructions to: assign a plurality of word identifiers (IDs), each of the word IDs being assigned to a different one of a plurality of words, each of the words appearing at least once in a plurality of search queries, each of the search queries comprising one or more of the words, wherein the plurality of search queries comprise a plurality of cached search queries that have been previously submitted to a search engine; assign a plurality of page IDs, each of the page IDs being assigned to a different one of a plurality of web pages, each of the web pages being included at least once in a plurality of search results generated in response to the search queries, each of the search results comprising one or more of the web pages; obtain a plurality of query IDs, each of the query IDs identifying a different one of the search queries, each of the query IDs being obtained by combining the word IDs identifying the words comprised in the search query identified by the query ID; and construct a BDD representing the search queries and the search results, the BDD comprising: a binary 0 terminal node; a binary 1 terminal node; and a plurality of paths, each path comprising a plurality of decision nodes and leading to either the 0 terminal node or the 1 terminal node, each decision node represents a binary digit in one of the query IDs or one of the page IDs in binary format, and for each of the paths that leads to the 1 terminal node, a web page represented by first one or more of the decision nodes on the path is included in a search result for a search query represented by second one or more of the decision nodes on the path.
58. The system of claim 56 , wherein the one or more processors are further operable, when executing the instructions, to: construct a second BDD representing a second search query and a second search result generated in response to the second search query, the second search query comprising one or more of the words, the second search result comprising one or more of the web pages; add the second BDD to the BDD by performing an OR operation on the BDD and the second BDD.