1. A computer readable medium having stored thereon one or more sequences of instructions for causing one or more microprocessors to perform the steps for delivery of content from a corpus of data, the steps comprising: specifying a rule having a trigger that identifies at least one characteristic corresponding to a plurality of items in a corpus of data; defining a content presentation action to be performed responsively to the trigger; receiving a search query for searching the corpus; generating a result set in response to the search query, the search query result set including one or more items from the corpus; determining a percentage of items in the search query result set that correspond to said at least one characteristic; identifying a threshold percentage, wherein the threshold percentage is a predetermined percentage of the total number of items in the search query result set; comparing the determined percentage of items to the threshold percentage; and presenting content in accordance with the content specification action when the determined percentage of items exceeds the threshold percentage.