14. A method according to claim 12 , wherein the step of blending the user profile with the current document summary comprises the step of, separately for each given one of a plurality of concepts included in both the user profile and the current document summary, averaging the relative strength identified for the given concept in the user profile with the relative strength identified for the given concept in the current document summary, each weighted by a respective blend factor.
14. A method according to claim 12 , wherein the step of blending the user profile with the current document summary comprises the step of, separately for each given one of a plurality of concepts included in both the user profile and the current document summary, averaging the relative strength identified for the given concept in the user profile with the relative strength identified for the given concept in the current document summary, each weighted by a respective blend factor. 15. A method according to claim 14 , wherein the blend factor is the same for all concepts in the plurality of concepts included in both the user profile and the current document summary.