Ran across this and it took me a while because of the dot notation that they are using in the path, seems you can just ignore it and use it as part of the path.
<quer:filtering xmlns:quer="http://www.taleo.com/ws/integration/query"> <quer:or> <quer:equal> <quer:field path="Candidate,History,ApplicationTrackingHistoryItem.CreationDate"/> <quer:query projectedClass="Application" alias="histItemSubQuery"> <quer:projections> <quer:projection> <quer:maximum> <quer:field path="Candidate,History,ApplicationTrackingHistoryItem.CreationDate"/> </quer:maximum> </quer:projection> </quer:projections> <quer:filterings> <quer:filtering> <quer:equal> <quer:field ownerQuery="histItemSubQuery" path="Number"/> <quer:field ownerQuery="NewHire" path="Number"/> </quer:equal> </quer:filtering> </quer:filterings> </quer:query> </quer:equal> <quer:isNull> <quer:field path="Candidate,History,ApplicationTrackingHistoryItem.CreationDate"/> </quer:isNull> </quer:or> </quer:filtering>