14. A computer implemented method according to claim 13 wherein said document element classes comprise logical element classes, each logical element class representing a logical operator, wherein the document elements of a logical element class comprise one or more text strings used to express the respective logical operator.
15. A computer implemented method according to claim 14 wherein said plurality of document element classes includes one or more of a multiple requirement class, a choice of requirement class and a conditional requirement class; wherein each document element in said multiple requirement class is a word or phrase indicative of the logical operator “and”; wherein each document element in said choice of requirement class is a word or phrase indicative of the logical operator “or”; and wherein each document element in said conditional requirement class is a word or phrase indicative of the logical operator “if”.