[torben-friis]

>I'm not sure why orders/purchases/subscriptions would be seen as mutable. At some point in time, customer X decided to exchange money amount M for a subscription Y.

Think for example about orders where a costumer bought three items and later cancelled one, the order value mutates as it is updated and at most we have a copy of the previous order state before price was updated (for some cases not even that).

If you think that’s not a good modeling for financial processes, well so do I, it’s the legacy we’re supposed to manage; moving out from that type of non ideal system to something more solid is what I’m researching.

[mrngm]

I suppose that's a flexible way of looking at orders, but it sounds more like a shopping basket. What if the customer ordered three items, you started shipping those, then the customer cancels one item. That sounds like the wrong order (hah) of things.