3. The system of claim 1 , wherein the semantically-enhanced statistical lookup data includes a plurality of entries, including for each of a plurality of topics a plurality of keyphrases associated with that topic, together with an indication or factor as to whether that keyphrase is sufficient and whether that keyphrase is necessary, and optionally an indication or factor as to the keyphrase's entropy.
3. The system of claim 1 , wherein the semantically-enhanced statistical lookup data includes a plurality of entries, including for each of a plurality of topics a plurality of keyphrases associated with that topic, together with an indication or factor as to whether that keyphrase is sufficient and whether that keyphrase is necessary, and optionally an indication or factor as to the keyphrase's entropy. 4. The system of claim 3 , wherein the sufficient, necessary and entropy factors can be simple Boolean (on/off) values, or alternatively, the factors can include a weighting or a scaled value between 0 and 1 for each topic, and the system can be configured to understand that particular values are indicative of the phrase being, necessary, sufficient, or of higher or lower entropy.