15. Data-processing apparatus according to claim 14 , wherein the lexicon comprises data concerning the species of subcellular entities having a particular identifier, wherein the data-processing apparatus is operable to determine whether the said group of one or more candidate identifiers comprises a plurality of candidate identifiers, and if so, to revise the group to produce a group comprising only identifiers, selected from the said group of one or more candidate identifiers, for which the species of the subcellular entity referred to by the identifiers is the identified species of the mention of the subcellular entity, thereby taking into account the identified species of the said individual mention of a subcellular entity.
15. Data-processing apparatus according to claim 14 , wherein the lexicon comprises data concerning the species of subcellular entities having a particular identifier, wherein the data-processing apparatus is operable to determine whether the said group of one or more candidate identifiers comprises a plurality of candidate identifiers, and if so, to revise the group to produce a group comprising only identifiers, selected from the said group of one or more candidate identifiers, for which the species of the subcellular entity referred to by the identifiers is the identified species of the mention of the subcellular entity, thereby taking into account the identified species of the said individual mention of a subcellular entity. 16. Data-processing apparatus according to claim 15 , wherein the second selection module is operable to select an identifier from the group of one or more candidate identifiers, or a revised group of candidate identifiers selected from the said group of one or more candidate identifiers, and to assign the selected identifier to an individual mention of a subcellular entity on the basis of a predetermined algorithm or heuristic.