31. The system of claim 16 , wherein the search engine system's web crawl order scheduler further comprises: instructions for-updating the web crawl interval of a document after retrieving a new copy of the document's content from its host and detecting content changes to the document based on the new copy.
31. The system of claim 16 , wherein the search engine system's web crawl order scheduler further comprises: instructions for-updating the web crawl interval of a document after retrieving a new copy of the document's content from its host and detecting content changes to the document based on the new copy. 33. The system of claim 31 , wherein the search engine system's web crawl order scheduler further comprises: instructions for identifying a first average interval between times where the document's content has not changed; instructions for identifying a second average interval between times where the document's content has changed; and instructions for updating the web crawl interval of the document based on the first average interval and the second average interval.