1. A machine-implemented method comprising: identifying, in a machine-readable index, a first sentence fragment and a second sentence fragment that are both associated with a same first information item, wherein the first information item is one of a date, an entity name, and a concept, wherein the index comprises a plurality of information items and sentence fragments associated with respective of the information items; in response to identifying that the first sentence fragment and the second sentence fragment are both associated with the same first information item, identifying a paraphrase pair in the first and second sentence fragments; repeating the identifying of the first sentence fragment and the second sentence fragment and the identifying of the paraphrase pair to identify a plurality of paraphrase pairs; and determining a frequency of occurrence value for each of the paraphrase pairs, wherein the frequency of occurrence value embodies the frequency at which each paraphrase pair appears in the plurality of paraphrase pairs, wherein the paraphrase pair comprises a first paraphrase and a second paraphrase, the first paraphrase comprises a proper subset of the words in the first sentence fragment, the second paraphrase comprises a proper subset of the words in the second sentence fragment, the first paraphrase and the second paraphrase are in a same language, have a same or a similar meaning, and are not identical, and the first and second sentence fragments and the paraphrase pair are identified by one or more data processors that perform actions under the instruction of computer-readable instructions.
5. The method of claim 1 , further comprising: identifying a subset of the plurality of paraphrase pairs having a frequency of occurrence value above a threshold; and adding the subset of the plurality of paraphrase pairs to a machine-readable data collection.