4. The method of claim 1 , wherein: the first term relationship score is changed in response to changing the content associated with the first document; and the second term relationship score is a term relationship score with respect to the common keyword of the changed content.
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 and a first contribution score, the first contribution 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 is linked by a link to the second document, wherein the first term relationship score is determined based on content of the first document and the link, and wherein updating the document rank score comprises determining whether each of a plurality of contribution scores is greater than a predetermined threshold value, whereby if one of the contribution scores is less than or equal to the predetermined threshold value, that contribution score is set to a zero value.