23. A system for extracting structured knowledge from unstructured text for use in a knowledge representation system, the knowledge representation system comprising a knowledge base that represents knowledge using a structured, machine-readable format, the structured, machine-readable format comprising fact triples, the system comprising one or more computing devices configured to: identify sentences in the unstructured text; convert each of a subset of the sentences to one or more simplified assertion statements of the form: subject noun phrase, verb phrase, object noun phrase; convert each of a subset of the simplified assertion statements to a corresponding fact triple, each fact triple being constructed from three knowledge base objects, the three knowledge base objects comprising two entity objects and a relationship object expressing a relationship between the two entity objects; and group the fact triples into a plurality of quarantine groups such that each of the fact triples is included in more than one of the quarantine groups, each quarantine group being defined by a corresponding one of a plurality of fact characteristics, a first one of the fact characteristics being that all of the fact triples in the corresponding quarantine group include a same one of the entity objects, a second one of the fact characteristics being that all of the fact triples in the corresponding quarantine group include a same one of the relationship objects; determine a reliability for each quarantine group with reference to the knowledge base; determine that more than one of the quarantine groups in which a first fact triple is included has at least a specified reliability; and classify the first fact triple as a reliable fact triple in response to determining that more than one of the quarantine groups in which the first fact triple is included has at least the specified reliability.
35. The system of claim 23 wherein the one or more computing devices are configured to: group the fact triples into a plurality of quarantine groups by adding each fact triple to a plurality of fact buckets, each fact bucket being defined by the corresponding fact characteristic shared by all fact triples added to that fact bucket; and wherein the one or more computing devices are configured to determine the reliability for each quarantine group by: for each fact bucket, determining whether each of a first number of fact triples added to that fact bucket is true or false with respect to the knowledge base; and designating each fact bucket as one of reliable, unreliable, or unknown based on one or both of a first number of fact triples added to that fact bucket determined to be false, or a second number of fact triples added to that fact bucket determined to be true.