Transactions

An important distinction between ledger solutions is the transaction model they uses underneath.

There are multiple options there, the key distinctions you'll find in the wild being the number of postings per transactions and the number of i/o per postings. Formance uses single i/o postings with multi-postings transactions.

Postings

In Formance and in general, postings model the movement of an amount of an asset from one account to another, e.g. Alice giving 100 coins to Bob:

{
  "source": "alice",
  "destination": "bob",
  "asset": "COIN",
  "amount": 100
}

Transactions

In Formance, transactions model the wrapping of postings with the intent of committing them atomically, e.g. Alice trading coins for gems over the counter:

{
  "postings": [
    {
      "source": "alice",
      "destination": "teller",
      "amount": 100,
      "asset": "COIN"
    },
    {
      "source": "teller",
      "destination": "alice",
      "amount": 5,
      "asset": "GEM"
    }
  ]
}

The rationale behind single i/o postings w/ multi-postings transactions originates from Formance's goal: help developers build sound financial applications, and supported by these observations:

• Multi-postings transactions allows the ledger to leverage atomicity to reduce the complexity on your side to handle complex transactions, e.g credit this user of X coin by funding the credit from multiple other accounts.

• While mathematically correct, multi i/o postings are inherently hard to grasp mentally and make auditability a challenge, which goes against our stated goal.

• In any-case, if needed, multi-postings transactions can be used to model multi i/o postings - by using a transient account, that receives all funds and resends them in a single transaction