1. A method, performed by one or more server devices, the method comprising: identifying, by one or more processors of the one or more server devices, a set of second documents that each contains a link to a first document; determining, by one or more processors of the one or more server devices, a freshness attribute associated with each document of the set of second documents; assigning, by one or more processors of the one or more server devices, a freshness score to the first document based on the freshness attribute associated with each document of the set of second documents; and ranking, by one or more processors of the one or more server devices, the first document with respect to at least one other document based on the freshness score assigned to the first document.