21. Apparatus as defined by claim 19 wherein said string matching means is operative to identify, at each segment of a string, the sequence of vocabulary words which provides the highest overall correlation up to that particular segment of the string when considering said particular segment and all previous segments of the string as being part of sequences of different word lengths.
21. Apparatus as defined by claim 19 wherein said string matching means is operative to identify, at each segment of a string, the sequence of vocabulary words which provides the highest overall correlation up to that particular segment of the string when considering said particular segment and all previous segments of the string as being part of sequences of different word lengths. 23. Apparatus as defined by claim 21 wherein said string matching means is also operative to store the highest overall correlation scores up to each segment, said scores being used in determining the highest overall correlation scores to subsequent segments.