span elements within nav elements

[murata2makoto]

http://www.idpf.org/epub/31/spec/epub-packages.html#confreq-nav-a

Each list item of the ordered list represents a heading, structure or other item of interest, and must contain either a child a element or a child span element. The a element describes the target that the link points to. The span element serves as a heading for breaking down lists into distinct groups (for example, a large list of illustrations can be segmented into several lists, one for each chapter).

Is <nav epub:type="toc"><ol><li><span>foo</span></li></ol></nav> allowed? In other words, can we have a <span>without sibling <a> elements or <ol> elements?

[rdeltour]

Is <nav epub:type="toc"><ol><li><span>foo</span></li></ol></nav> allowed? In other words, can we have a <span> without sibling <a> elements or <ol> elements?

No. A following bullet says:

The span element must be followed by an ol ordered list; it cannot be used in "leaf" li elements.

[murata2makoto]

Yes, you are right. The sentence you quoted disallows my example shown above.

But I think that we have to be more explicit. I was confused, and I know that one implementor was confused too.

nav/ol/li can have either an a element possibly followed by a single ol element, or a span element followed by a single ol element. Other than whitespace, no text chunk is allowed to occur as a child of nav/ol/li.

[mattgarrish]

I don't see more prose is going to make it easier to read.

A content model box to the start of the section would probably be better, like this:

[mattgarrish]

I think we can also remove the duplicative content model prose if we do this. See a possible rewrite here:
https://docs.google.com/document/d/1l96NqIYEun1dzuepGELsfmnbwucLv4nIKfoWlWJWUds/edit#heading=h.wuwozrqhc3jm

[mattgarrish]

Proposed Solution

Add a content model box and update the prose as suggested in the referenced google doc.