This should have posted Dec. 12. 2010, but I can find no JIRA record. It is from one of our teams during their planning review:
5.3.5 List Item Style Rules
The first line in a list item is preceded by a bullet or number, depending on the list style assigned to the list. If a list item starts another list and does not contain any text, no bullet or number is displayed.
The list style which is applied to a list need not contain a list level style for the list level the list item specifies. The following rules are applied to determine the list level style in this case
• If the list is contained in another list, the list level style defined in the list style which is applied to the surrounding list for the level of the item is used.
• If the list is not contained in another list or if no list level style is not defined by any of the list styles assigned to surrounding lists, the list level style defined by the default list style is used See 5.3.2.
The text:style-override attribute specifies an override to the list style to be applied to a list item.
In section 5.3.5 List Item Style Rules, the logic describes what to do when a list level is not defined as a part of a list style. We'd like to suggest that the logic be updated so that there is a better experience with list item overrides (mentioned in section 19.875).
If a list item is overridden, so that it points to a list style (List Style A) that is different from the rest of the list (List Style B), then it makes sense that perhaps List Style A does not define all the list levels. This is because only a small portion of List Style A would be used by the override and the rest of the levels would be unnecessary to describe the behavior of the overridden list item. Thus, if List Style A does not define all the levels, it would make sense that if a level is missing in List Style A, a consumer should assume that the missing level is defined by List Style B.