Question from keys review: cascading of metadata

DITAWeb URL:
http://ditaweb.com/oasis-dita/#/Collaborate/00160583-FA_1/DB00074542/Processing%20key%20references%20on%20%3Ctopicref%3E%20elements

Topic: "Processing key references on <topicref> elements"

Text in question, about combining metadata when @keyref is used on <topicref>:
Content from a key-defining element cascades to the key-referencing element following the rules for combining metadata between maps and other maps and between maps and topics. The @lockmeta attribute is honored when metadata content is combined. 

Original comment thread: 
[Chris Nitchie] The rules for map-to-map cascading are subtly different than the ones for parent-child topicrefs. Which should apply? 
[Robert Anderson] Agree that these are subtly different. The language is taken from 1.2 so we may not be able to resolve - depending on which one people gave more weight to, I think either could be considered correct. Language in 1.2: "Content from a key reference element and a key-defining element is combined following the rules for combining metadata between maps and other maps and between maps and topics. The @lockmeta attribute is honored when metadata content is combined." 
Robert D Anderson
IBM Authoring Tools Development
Chief Architect, DITA Open Toolkit (http://www.dita-ot.org/)