Metadata

When a new block is added, that block may have many transactions. Each block has automatically generated metadata, as does each transaction. You can also add custom metadata.

_block

Key	Description
number	Block number for this block.
hash	Hash for current block. Not included in block hash (can't include itself!).
prevHash	Previous block's hash
transactions	Reference to transactions included in this block (_tx).
ledgers	Reference to transactor auth identities that signed this block. Not included in block hash.
instant	Instant this block was created, per the transactor.
sigs	List of transactor signatures that signed this block (signature of _block/hash). Not included in block hash.

_tx

Key	Description
tempids	Tempid JSON map for this transaction.
sig	Signature of original JSON transaction command.
tx	Original JSON transaction command.
doc	Optional docstring for the transaction.
altId	Alternative Unique ID for the transaction that the user can supply. Transaction will throw if not unique.
nonce	A nonce that helps ensure identical transactions have unique txids, and also can be used for logic within smart functions (not yet implemented). Note this nonce does not enforce uniqueness, use _tx/altId if uniqueness must be enforced.
authority	If this transaction utilized an authority, reference to it.
auth	Reference to the auth id for this transaction.