|DITA map files / DITA map vocabulary|
If a ditamap includes a reference to a topic that does not exist, the publishing process will generate output with a broken link. It will not gracefully omit the reference. You should therefore take care to avoid these dangling topicref.
A dangling topicref is a reference in a ditamap to a topic that does not exist in the collection. If you comprehend a topicref to be a link, a dangling topicref is the same as a broken link.
You may expect that the processing process will cope gracefully with the missing reference, but that is not necessarily the case. In short, it is bad practice to have dangling topicref in a ditamap. A dangling topicref should be considered an authoring error, even though it is not, strictly speaking, an XML error.
Good file management practices will help avoid dangling topicrefs.