31. An apparatus, comprising: means for storing a collection of digital information in a first file; means for storing a query expression in a cache file, wherein the query expression specifies a subset of digital information to be retrieved from the collection of digital information in the first file; means for retrieving the subset of digital information from the collection of digital information in the first file, wherein said retrieving comprises parsing the collection of digital information in the first file according to the query expression; means for storing a currency token in association with the cache file, wherein the currency token indicates whether the cache file is current; means for storing the retrieved subset of the collection of digital information in the cache file, wherein the subset of the collection of digital information is stored in association with the stored query expression; and wherein the currency token includes an attribute of the first file, and wherein the attribute describes the first file at a time when the collection of digital information stored in the first file is parsed to generate the subset of the collection of digital information which is stored in the cache file.
31. An apparatus, comprising: means for storing a collection of digital information in a first file; means for storing a query expression in a cache file, wherein the query expression specifies a subset of digital information to be retrieved from the collection of digital information in the first file; means for retrieving the subset of digital information from the collection of digital information in the first file, wherein said retrieving comprises parsing the collection of digital information in the first file according to the query expression; means for storing a currency token in association with the cache file, wherein the currency token indicates whether the cache file is current; means for storing the retrieved subset of the collection of digital information in the cache file, wherein the subset of the collection of digital information is stored in association with the stored query expression; and wherein the currency token includes an attribute of the first file, and wherein the attribute describes the first file at a time when the collection of digital information stored in the first file is parsed to generate the subset of the collection of digital information which is stored in the cache file. 32. The apparatus of claim 31 , wherein the means for storing the collection of digital information comprises means for storing a plurality of entries in an XML format.