15. A computer system comprising: one or more computing devices; an interface at the one or more computing devices that is programmed to receive a query; a knowledge repository that is accessible to the one or more computing devices and that includes a plurality of topics, each topic including one or more attributes and associated values for the attributes; a mapping module that is installed on the one or more computing devices and that identifies one or more candidate topics from the topics in the knowledge repository, wherein the identified candidate topics are determined to relate to a possible subject of the query; an answer generator that is installed on the one or more computing devices and that generates, for each candidate topic, a candidate topic-answer pair that includes (i) the candidate topic, and (ii) an answer to the query for the candidate topic, wherein the answer for each candidate topic is identified from information in the knowledge repository; a search engine that is installed on the one or more computing devices and that returns search results based on the query, wherein one or more of the search results references an annotated resource, wherein an annotated resource is a resource that, based on an automated evaluation of the content of the resource, is associated with an annotation that identifies one or more likely topics associated with the resource; a scoring module that is installed on the one or more computing devices and that determines a score for each candidate topic-answer pair based on (i) an occurrence of the candidate topic in the annotations of the resources referenced by one or more of the search results, and (ii) an occurrence of the answer in annotations of the resources referenced by the one or more search results, or in the resources referenced by the one or more search results; and a front end system at the one or more computing devices that determines whether to respond to the query with one or more answers from the candidate topic-answer pairs, based on the scores.
15. A computer system comprising: one or more computing devices; an interface at the one or more computing devices that is programmed to receive a query; a knowledge repository that is accessible to the one or more computing devices and that includes a plurality of topics, each topic including one or more attributes and associated values for the attributes; a mapping module that is installed on the one or more computing devices and that identifies one or more candidate topics from the topics in the knowledge repository, wherein the identified candidate topics are determined to relate to a possible subject of the query; an answer generator that is installed on the one or more computing devices and that generates, for each candidate topic, a candidate topic-answer pair that includes (i) the candidate topic, and (ii) an answer to the query for the candidate topic, wherein the answer for each candidate topic is identified from information in the knowledge repository; a search engine that is installed on the one or more computing devices and that returns search results based on the query, wherein one or more of the search results references an annotated resource, wherein an annotated resource is a resource that, based on an automated evaluation of the content of the resource, is associated with an annotation that identifies one or more likely topics associated with the resource; a scoring module that is installed on the one or more computing devices and that determines a score for each candidate topic-answer pair based on (i) an occurrence of the candidate topic in the annotations of the resources referenced by one or more of the search results, and (ii) an occurrence of the answer in annotations of the resources referenced by the one or more search results, or in the resources referenced by the one or more search results; and a front end system at the one or more computing devices that determines whether to respond to the query with one or more answers from the candidate topic-answer pairs, based on the scores. 16. The computer system of claim 15 , wherein the front end system determines whether to respond to the query based on a comparison of one or more of the scores to a predetermined threshold.