Your Ledger Stores Balances. I Built One That Stores Intentions.
There is a subtle way to get purpose-bound money wrong, and it is the cleanest way I know to explain why I changed what a ledger stores.
A charity raises money for a cause. It spends some, writes up what it did, and publishes that report. Someone authorized to check the report signs off, and the sign-off releases budget for spending. That part is fine.
The trouble is with the next donation. If the sign-off simply switched spending on, then every unit of money that arrives afterwards would be covered by an approval it was never part of. One check, done once, would quietly turn into standing permission to spend everything that comes later.
A naive design walks straight into this. Getting the interaction right is most of the work, and it forced two changes to how the ledger behaves: what it is allowed to store, and when it is...
Copyright of this story solely belongs to hackernoon.com. To see the full text click HERE
