1. A method of scheduling document indexing, comprising: at a computing system having one or more processors and memory storing programs for execution by the one or more processors: retrieving a number of document identifiers, each document identifier identifying a corresponding document on a network; and for each retrieved document identifier and its corresponding document, determining a query-independent score indicative of a rank of the corresponding document relative to other documents in a set of documents; determining a first score for the document identifier that is a function of the determined query-independent score, a determined content change frequency of the corresponding document, and an age of the corresponding document; comparing the first score against a threshold value thereby obtaining a result, wherein the threshold value is a function of a speed of the engine crawler system; and conditionally scheduling the corresponding document for indexing based on the result.
1. A method of scheduling document indexing, comprising: at a computing system having one or more processors and memory storing programs for execution by the one or more processors: retrieving a number of document identifiers, each document identifier identifying a corresponding document on a network; and for each retrieved document identifier and its corresponding document, determining a query-independent score indicative of a rank of the corresponding document relative to other documents in a set of documents; determining a first score for the document identifier that is a function of the determined query-independent score, a determined content change frequency of the corresponding document, and an age of the corresponding document; comparing the first score against a threshold value thereby obtaining a result, wherein the threshold value is a function of a speed of the engine crawler system; and conditionally scheduling the corresponding document for indexing based on the result. 6. The method of claim 1 , wherein the first score for the document identifier is a function of an age of the corresponding document.