Can we do this in XML?

Parallel markup "I believe that sequential formatted objects are best represented by a format in which the text and the markup are treated as separate parallel members, presumably (but not necessarily) in different files. The tags can be like those of SGML, but they are not embedded in the text itself."
Ranges Using character ranges, we can reference the text from a separate file. I used (start, end) but other alternatives include (start, length) or just (offset from the previous) - Nelson recommends the last of these.
Still hierarchical, but... The markup itself must be hierarchical, but two forms of overlap are possible. Multiple markup documents may of course provide completely different markup for the text, or a single markup document may point repeatedly to the same or overlapping pieces of text.
To and from regular XML One process separates text and markup (with an optional clean-up process), while another process permits the recombination of text and markup for use in more traditional XML contexts.