14. A system comprising one or more computers and one or more storage devices storing instructions that when executed by the one or more computers cause the one or more computers to perform operations comprising: obtaining data identifying a set of seed fact pairs, wherein each seed fact pair associates a fact subject phrase with an information phrase; determining that a first sentence matches a first seed fact pair in the set of seed fact pairs, wherein determining that the first sentence matches the first seed fact pair comprises determining that the fact subject phrase and the information phrase from the first seed pair fact both occur in the first sentence separated by one or more terms; extracting, from the first sentence a basic infix-only pattern that includes the one or more terms that separate the fact subject phrase from the information phrase in the first sentence; generating a generalized infix-only extraction pattern from the basic infix-only pattern, wherein generating the generalized infix-only extraction pattern from the basic infix-only pattern comprises: determining that a first term of the one or more terms that separate the fact subject phrase from the information phrase in the first sentence belongs to a first distributionally similar class, and substituting the first distributionally similar class for the first term in the basic infix-only pattern; determining that a second sentence matches the generalized infix-only pattern, comprising determining that the second sentence includes a term that belongs to the first distributionally similar class; and applying the generalized infix-only pattern to the second sentence to extract a candidate fact pair from the second sentence.
14. A system comprising one or more computers and one or more storage devices storing instructions that when executed by the one or more computers cause the one or more computers to perform operations comprising: obtaining data identifying a set of seed fact pairs, wherein each seed fact pair associates a fact subject phrase with an information phrase; determining that a first sentence matches a first seed fact pair in the set of seed fact pairs, wherein determining that the first sentence matches the first seed fact pair comprises determining that the fact subject phrase and the information phrase from the first seed pair fact both occur in the first sentence separated by one or more terms; extracting, from the first sentence a basic infix-only pattern that includes the one or more terms that separate the fact subject phrase from the information phrase in the first sentence; generating a generalized infix-only extraction pattern from the basic infix-only pattern, wherein generating the generalized infix-only extraction pattern from the basic infix-only pattern comprises: determining that a first term of the one or more terms that separate the fact subject phrase from the information phrase in the first sentence belongs to a first distributionally similar class, and substituting the first distributionally similar class for the first term in the basic infix-only pattern; determining that a second sentence matches the generalized infix-only pattern, comprising determining that the second sentence includes a term that belongs to the first distributionally similar class; and applying the generalized infix-only pattern to the second sentence to extract a candidate fact pair from the second sentence. 16. The system of claim 14 , the operations further comprising: tagging each word in the fact subject phrase and the information phrase from the first seed fact pair with a respective part-of-speech tag; generating a first sequence of part-of-speech tags for the fact subject phrase of the first seed fact pair and a second sequence of part-of-speech tags for the information phrase of the first seed fact pair, wherein applying the generalized infix-only pattern to the second sentence to extract the candidate fact pair comprises: beginning with a word adjacent to a first end of the infix-only pattern and proceeding away from the pattern in the second sentence, adding a word from the second sentence to a first phrase for each tag in the second sequence, the first phrase being the portion of the second sentence between the last word added and the pattern, each word added to the phrase having a part of speech that matches the part of speech of the corresponding tag in the first sequence; and beginning with a word adjacent to a second end of the infix-only pattern and proceeding away from the pattern in the second sentence, adding a word from the second sentence to a second phrase for each tag in the second sequence, the second phrase being the portion of the second sentence between the last word added and the pattern, each word added to the phrase having a part of speech that matches the part of speech of the corresponding tag in the second sequence; wherein the candidate fact pair comprises the first phrase and the second phrase.