Any ideas how i'de write some engine to figure out relationships between topics on teh intarwebs?

suggestions high or low level etc? This is an application of Ontology right?

ie, learn that drupal is related to php, civicrm is related to drupal (civicrm is a sideproject using drupal)

could do straight keyword analyses but im not sure thats the way

or is this the same 'holy grail' that search engines are trying todo? ie figure out that a dog is an animal, and the dog subject is related to animal?