ATK has the following relation types:

ATK_RELATION_DETAILS
Reciprocal of ATK_RELATION_DETAILS_FOR. Indicates that this object has a detailed or extended description, the contents of which can be found in the target object(s). This relation type is most appropriate for information that is sufficiently lengthy as to make navigation to the container of that information desirable. For less verbose information suitable for announcement only, see ATK_RELATION_DESCRIBED_BY. If the detailed information describes an error condition, ATK_RELATION_ERROR_FOR should be used instead. Since : ATK-2.26.

ATK_RELATION_DETAILS_FOR
Reciprocal of ATK_RELATION_DETAILS. Indicates that this object provides a detailed or extended description about the target object(s). See also ATK_RELATION_DESCRIPTION_FOR and ATK_RELATION_ERROR_FOR. Since : ATK-2.26.

These should be included in the implementations of the details and summary elements so that Orca can quickly figure out what information should be presented upon expansion of the element.