Observation groups are a way of grouping multiple observation under a single one. Webservices Obs resource supports observation groups using the tags "obsGroup" and "groupMembers". But this does not seem to work. Tried two ways of creating an observation group
Create the observations along with a parent observation. Here only the parent is pre-created
All the observations are pre-created and an observation group is created.
As Darius mentioned over email, the observation groups should be created like in Method 1. Also, in my view, none of the observations should be pre-created. In which case, the type of obsGroup be boolean indicating whether observation groups exist or not. Even better, there is no need for obsGroup field at all.