Abstract: The invention disclosed herein is a method of checking the validity of a set of digital information contained in an information cache connected to an information source. The method includes specifying two or more overlapping supersets of information having the set of digital information as a common subset; and performing the validity check of the set of digital information by comparing validity information associated with one or more of the supersets in the cache and validity information associated with corresponding supersets in the information source. Disclosed herein is a method of and apparatus for retrieving digital information from an information source having a cache connected thereto.