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62 lines
4.0 KiB
ReStructuredText
Vault
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=====
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.. toctree::
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:maxdepth: 1
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soft-locking.rst
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The vault contains data extracted from the ledger that is considered relevant to the node’s owner, stored in a relational model
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that can be easily queried and worked with.
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The vault keeps track of both unconsumed and consumed states:
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* **Unconsumed** (or unspent) states represent fungible states available for spending (including spend-to-self transactions)
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and linear states available for evolution (eg. in response to a lifecycle event on a deal) or transfer to another party.
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* **Consumed** (or spent) states represent ledger immutable state for the purpose of transaction reporting, audit and archival, including the ability to perform joins with app-private data (like customer notes).
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By fungible we refer to assets of measurable quantity (eg. a cash currency, units of stock) which can be combined
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together to represent a single ledger state.
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Like with a cryptocurrency wallet, the Corda vault can create transactions that send value (eg. transfer of state) to
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someone else by combining fungible states and possibly adding a change output that makes the values balance (this
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process is usually referred to as ‘coin selection’). Vault spending ensures that transactions respect the fungibility
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rules in order to ensure that the issuer and reference data is preserved as the assets pass from hand to hand.
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A feature called **soft locking** provides the ability to automatically or explicitly reserve states to prevent
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multiple transactions within the same node from trying to use the same output simultaneously. Whilst this scenario would
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ultimately be detected by a notary, *soft locking* provides a mechanism of early detection for such unwarranted and
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invalid scenarios. :doc:`soft-locking` describes this feature in detail.
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.. note:: Basic 'coin selection' is currently implemented. Future work includes fungible state optimisation (splitting and
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merging of states in the background), and 'state re-issuance' (sending of states back to the
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issuer for re-issuance, thus pruning long transaction chains and improving privacy).
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There is also a facility for attaching descriptive textual notes against any transaction stored in the vault.
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The vault supports the management of data in both authoritative ("on-ledger") form and, where appropriate, shadow ("off-ledger") form:
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* "On-ledger" data refers to distributed ledger state (cash, deals, trades) to which a firm is participant.
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* "Off-ledger" data refers to a firm's internal reference, static and systems data.
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The following diagram illustrates the breakdown of the vault into sub-system components:
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.. image:: resources/vault.png
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Note the following:
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* The vault "On Ledger" store tracks unconsumed state and is updated internally by the node upon recording of a transaction on the ledger
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(following successful smart contract verification and signature by all participants).
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* The vault "Off Ledger" store refers to additional data added by the node owner subsequent to transaction recording.
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* The vault performs fungible state spending (and in future, fungible state optimisation management including merging, splitting and re-issuance).
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* Vault extensions represent additional custom plugin code a developer may write to query specific custom contract state attributes.
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* Customer "Off Ledger" (private store) represents internal organisational data that may be joined with the vault data to perform additional reporting or processing.
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* A :doc:`Vault Query API </api-vault-query>` is exposed to developers using standard Corda RPC and CorDapp plugin mechanisms.
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* A vault update API is internally used by transaction recording flows.
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* The vault database schemas are directly accessible via JDBC for customer joins and queries.
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Section 8 of the `Technical white paper`_ describes features of the vault yet to be implemented including private key management, state splitting and merging, asset re-issuance and node event scheduling.
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.. _`Technical white paper`: _static/corda-technical-whitepaper.pdf
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