The bussiness domain of Pledger.io

The diagram below depicts the domain model that is used in Pledger.io. In this domain you can clearly see that the Transaction is linked to the Account using at least two Parts. It also indicates that there are multiple concepts that describe the context of a transaction, these are:

In this design the choice was made to attach everything on a UserAccount. Where the Account is the primary entity, with an enumeration in it to indicate the type of account.