16. The apparatus of claim 13 , wherein: the first series of one or more words includes two or more words and the second series of one or more words includes two or more words; and the determining a second series of one or more words comprises determining a second series that includes a word that is included in the first series.
13. An apparatus comprising: at least one processor; and at least one storage medium having encoded thereon processor-executable instructions that, when executed by the at least one processor, cause the at least one processor to carry out a method of processing a plurality of expressions each having a medical meaning, each expression comprising a series of one or more words, the method comprising: extracting from a first expression at least one first clinical fact relating to the medical meaning of the first expression; extracting from a second expression at least one second clinical fact relating to the medical meaning of the second expression; determining whether the at least one first clinical fact and the second clinical fact have inconsistent medical meanings; and in response to determining that the at least one first clinical fact and the at least one second clinical fact have inconsistent medical meanings, determining a first series of one or more words related to the at least one first clinical fact, the first series being in the first expression and not in the second expression, determining a second series of one or more words related to the at least one second clinical fact, the second series being in the second expression and not in the first expression, and adding the first series and the second series to a set of series of words and associating the first series with the second series in the set.