I was at the Reading Room at the University of Washington a couple of weeks ago (https://lib.uw.edu/suzzallo/study/study-spaces/reading-room/) and took the opportunity to grab some books more or less at random and look at their indexes to see how they handled page numbers for non-leave index entries. The results are attached.
It's a small sample, of course, but two of the samples have numbers on both the top-level entry and subordinate entries and one only has numbers on the 2nd-level entries. I didn't have a lot of time so I wasn't able to search out a sample with a 3-level index.
But this definitely demonstrates that there are examples of both approaches to indexes in published works, meaning it would be inappropriate for the DITA standard to impose a rule.
Cheers,
E.



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Eliot Kimber
Sr Staff Content Engineer
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