1. A method that uses a processor to determine a document rank, comprising: calculating, using the processor, a document rank score of a second document based on a first term relationship score of a first document, the first term relationship score being determined based on a common keyword between the first document and the second document; changing the first term relationship score to a second term relationship score; and updating the document rank score of the second document based on the second term relationship score, wherein the first document comprises a link to the second document.