indexterm: primary optional

Back a couple of years ago, RFE 2900458, "Make xml:id required on start-of-range index terms," was filed and deferred to 6.0 to avoid backwards compatibility problems (I'm not quite sure what the incompatibility was). Here is the link:

https://sourceforge.net/tracker/index.php?func=detail&aid=2900458&group_id=21935&atid=384107

There is a related issue that I've run into, and I want to see if it is also backwards incompatible or if it can be handled earlier.

Right now, it is legal to have a completely empty <indexterm/> (i.e., no content and no attributes) or to have an <indexterm> with a <secondary> element but no <primary> element, for example the following two statements are valid:

<indexterm/>
<indexterm><secondary>some term</secondary</indexterm>

It turns out that if class="endofrange", then <indexterm> must be empty, but the reverse isn't true. That is, all <indexterms> except those with class="endofrange" should require at least a <primary> element, but they do not.

So, the question I have is whether this situation should be lumped into the previous RFE and turn it into a general "clean up index term" RFE for 6.0, or are there parts that could be handled in an earlier release?

Either way, I'm glad to either create a new RFE or update the current one.

Best Regards,
Dick Hamilton
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