22. The apparatus set forth in claim 21 wherein: the digital documents include both structural information and content information and a fingerprint for a document of the documents comprises: a structural encoding portion in which a first encoding preserves semantic information about components of the digital document's structural information; and a content encoding portion in which a second encoding preserves content information about components of the digital document's content.
22. The apparatus set forth in claim 21 wherein: the digital documents include both structural information and content information and a fingerprint for a document of the documents comprises: a structural encoding portion in which a first encoding preserves semantic information about components of the digital document's structural information; and a content encoding portion in which a second encoding preserves content information about components of the digital document's content. 24. The apparatus set forth in claim 22 wherein the instructions are further executed by the processor to: (a). find an encoding of structural information in a first fingerprint; (b). find a second fingerprint substring matching a first fingerprint substring that begins at the found encoding; (c). add a length of the found substring to a running length total; (d). find another encoding of structural information in the first fingerprint not contained in any found substring and repeating acts (a)-(c) with the other encoding of structural information in the first fingerprint; (e). repeat acts (a)-(d) until no further encodings of structural information can be found in act (d); and (f). use a length of one of the fingerprints and the running length total to compute a similarity value.