25. A system, comprising: a memory to store executable instructions; and one or more processors to execute the instructions to: determine a measure of how a content of a document changes over time, as a function of: an update frequency based on a number of updates of the content of the document over time, and an update amount based on: how much visible content of the document, out of a total amount of visible content of the document, has changed over time, and at least one of: a quantity of new pages added to the document over time, or a ratio of a quantity of new pages associated with the document over time versus a total quantity of pages associated with the document; generate a score for the document based, at least in part, on the measure of how the content of the document changes over time; and rank the document with regard to at least one other document based, at least in part, on the score.
25. A system, comprising: a memory to store executable instructions; and one or more processors to execute the instructions to: determine a measure of how a content of a document changes over time, as a function of: an update frequency based on a number of updates of the content of the document over time, and an update amount based on: how much visible content of the document, out of a total amount of visible content of the document, has changed over time, and at least one of: a quantity of new pages added to the document over time, or a ratio of a quantity of new pages associated with the document over time versus a total quantity of pages associated with the document; generate a score for the document based, at least in part, on the measure of how the content of the document changes over time; and rank the document with regard to at least one other document based, at least in part, on the score. 26. The system of claim 25 , where the update frequency is based on an average time between updates of the content of the document.