14.1 History Object - HistoryCollection
The terms "collection" and "HistoryCollection" seem sort of generic and confusing. How about "collectMode" and "HistoryCollectMode"

14.1 History Object - prototype
Glad to finally see something like this. However I am not quite sure how it works. I think we need an example.

14.2.4.2 History Query as Preformatted List
This design requires two separate round trip requests which is pretty terrible for performance. I think a requirement of this design is that once the history point is learned by the client system, that it can request history data with a single HTTP request. I don't see that having an oBIX XML response before getting the data provides much value. I would suggest this: just add a "format" field to the HistoryFilter object and when specified the result is returned in the requested MIME type.