xforms-action-error error types

In Setvalue, there are two cases of an xforms-action-error, with no  
indication of what the error-type should be:

https://www.w3.org/community/xformsusers/wiki/XForms_2.0#The_setvalue_Element

14.3 The setvalue Element
Element nodes: If element child nodes are present, then an  
xforms-action-error Event is dispatched;
the root node of an instance: an xforms-action-error Event occurs.

Suggestions?

Steven