Re: Value object with set of aggregate roots?

Good points, Thomas.

By "product" I do mean a third party product (a rule engine, to be precise). It performs calculations that conceptually could be placed within the domain it operates on, but for various reasons (most noticeably the fact that a rule engine enables business users to define the rules themselves) these are performed by this product.

You are right that this decision as such can be considered as a problems with our boundaries. It is another thing, however, to change this. The snapshot is part of the interface of this hexagon, so it should be the domain that is responsible for creation. In fact, this "picture" object is therefore part of our domain (and a separate context).