My model needs to take snapshots of certain data and to do this I have various snapshot classes.
Sometimes you might snapshot an aggregate root such as PurchaseOrder and expect all PurchaseOrderLines to be snapshotted along with it. Sometimes though the Parent/Child relationship is not part of an aggregate root and you want the child snapshot to create the parent snapshot, for example when snapshotting an Address you might want to snapshot the Country.
So when I was looking at my snapshot diagrams it wasn't immediately obviously which behaviour you get. Hans showed me this article: http://theblog.capableobjects.com/2009/12/catching-more-information-in-your-model.html
Now I have added symbols + tagged value definitions to my model and as a consequence the diagrams show me visually which way the snapshots work. Brilliant!