1. A recommended information presentation apparatus, comprising: a memory; and a processor that executes the following computer-executable components within the memory: a display unit configured to display text data; an extraction unit configured to extract keyword candidates from the text data; a storage unit configured to store semantic attributes of the keyword candidates, semantic attribute rules which contain scoring criteria for the semantic attributes, descriptive phrases extracted from the text data and describing the keyword candidates, and descriptive phrase rules which contain scoring criteria for the descriptive phrases based on respective determinations of interest in the descriptive phrases; a selection unit configured to calculate scores of the keyword candidates based on the semantic attribute rules and the descriptive phrase rules to select a selected keyword which has a highest score among the keyword candidates; a search unit configured to search an information database with the selected keyword and receive a search result; and a control unit configured to display the search result on the display unit as recommended information with regards to the text data.