7. A computer program product for using user preferences to customize answer output comprising: a computer readable, tangible storage device; and program instructions stored by the computer readable, tangible storage device, which, when executed by a processor, cause a computing platform to: for a first user and a first question: extract by a natural language processor from the question one or more user preferences and one or more sentiment levels; perform a semantic search on of the first question; receive a plurality of candidate answers from the semantic search; select one or more of the received candidate answers, wherein the selection is performed both according to the one or more sentiment levels and according to the one or more user preferences; and produce a first user output including the selected one or more candidate answers; for a second question and a second user, repeat the step of extracting preferences from the second question; accumulate the preferences and sentiments extracted from the second question with the preferences and sentiments extracted from the first question; and for the second question, repeat the steps of performing a semantic search, receiving candidate answers, selecting candidate answers according to the accumulated preferences and sentiments, and producing a second output.
7. A computer program product for using user preferences to customize answer output comprising: a computer readable, tangible storage device; and program instructions stored by the computer readable, tangible storage device, which, when executed by a processor, cause a computing platform to: for a first user and a first question: extract by a natural language processor from the question one or more user preferences and one or more sentiment levels; perform a semantic search on of the first question; receive a plurality of candidate answers from the semantic search; select one or more of the received candidate answers, wherein the selection is performed both according to the one or more sentiment levels and according to the one or more user preferences; and produce a first user output including the selected one or more candidate answers; for a second question and a second user, repeat the step of extracting preferences from the second question; accumulate the preferences and sentiments extracted from the second question with the preferences and sentiments extracted from the first question; and for the second question, repeat the steps of performing a semantic search, receiving candidate answers, selecting candidate answers according to the accumulated preferences and sentiments, and producing a second output. 8. The computer program product as set forth in claim 7 further comprising program instructions stored by the computer readable, tangible storage device, which, when executed by a processor, cause a computing platform to: for the first user and a third question, extract by a natural language processor one or more user preferences and one or more sentiment levels, wherein each user preference and each sentiment level is associated with the third question, or associated with the first user, or associated with both the third question and the first user; search semantically on the third question; receive a plurality of candidate answers from the semantic search on the third question; selecting by a computer one or more of the received candidate answers from the search on the third question, wherein the selection is performed according to a combination of the one or more sentiment levels and according to the one or more user preferences associated with the first and second users and with the first, second and third questions; and produce a third user output including the selected one or more candidate answers selected from the search on the third question.