Abstract: Method and apparatus for identifying particular desired information bearing records having desired predetermined identifiable characteristics from a set of such records in a base data file. A special retrieval file including arrays of binary coded elements is produced and maintained from the information content of the base data file. Each array of the retrieval file corresponds to a particular predetermined identifiable characteristic of language structure potentially present in or associated with the set of records concerned and each element in such an array corresponds to and is representative of the address or location of a particular one of the records in the base data file. The elements are binary coded to represent the presence or absence of the predetermined identifiable characteristics of language structure associated with that particular array in the corresponding record.