6. A method as set forth in claim 5 , performed as an iterative process comprising: for each iteration, repeating the selecting and associating of the lower-ordered and higher-ordered indexing text fragments for the low-order sub-set of the ordered sequence of indexing text fragments using the lower-ordered indexing text fragment of the previous iteration as the initial indexing text fragment; and for each iteration, repeating the selecting and associating of the lower-ordered and higher-ordered indexing text fragments for the high-order sub-set of the ordered sequence of indexing text fragments using the higher-ordered indexing text fragment of the previous iteration as the initial indexing text fragment.
5. A method as set forth in claim 1 , further comprising: selecting the lower-ordered indexing text fragment to be at about the middle of a low-order sub-set of the ordered sequence of indexing text fragments defined by the set of indexing text fragments at lower order than the initial indexing text fragment; and selecting the higher-ordered indexing text fragment to be at about the middle of a high-order sub-set of the ordered sequence of indexing text fragments defined by the set of indexing text fragments at higher order than the initial indexing text fragment.