1. A processing apparatus comprising: structured/hierarchical content, said apparatus makes a determination whether or not said structured/hierarchical content delivered through a network includes a content portion matched with a predetermined matching pattern, and performs predetermined processing for the structured/hierarchical content if a result of the determination is positive, the processing apparatus further comprising: target subtree setting means for setting a target subtree relating to a range including a target content portion as an extracted portion of the matching pattern in the structured/hierarchical content (hereinafter, referred to as a “target content”) from which the matching pattern is to be extracted; occurrence mode detecting means for detecting an occurrence mode of each node of the target subtree by selecting a plurality of past structured/hierarchical contents with respect to the target content and collating the target subtree relating to the target content with a tree relating to each of the past structured/hierarchical contents; statistical information generating means for generating statistical information concerning an occurrence frequency of the occurrence mode of each node in the target subtree based on the plurality of past structured/hierarchical contents; classifying means for performing classification of each node of the target subtree based on the statistical information and a result of detecting the occurrence mode; and matching pattern generating means for generating the matching pattern for the target content portion based on the classification.