Glossary
Key terms used throughout the Xian documentation.
A
ABCI
Application BlockChain Interface. The protocol that connects CometBFT (consensus) to the Xian application layer. Defines methods like CHECK_TX, FINALIZE_BLOCK, COMMIT, and QUERY.
B
Block
A batch of transactions ordered and agreed upon by validators through consensus. Each block has a height (sequential number), a hash, a timestamp, and a list of transactions.
C
Caller
The immediate caller of a contract function, available as ctx.caller. When a user calls a contract directly, ctx.caller is the user's address. When contract A calls contract B, ctx.caller inside B is the name of contract A.
CometBFT
The Byzantine Fault Tolerant consensus engine used by Xian (formerly known as Tendermint). Handles peer-to-peer networking, block proposal, and validator voting.
Construct
The @construct decorator marks a function that runs once when a contract is deployed. It initializes state and is never callable again after deployment.
Contract
A Python source file deployed to the Xian blockchain. Contains state declarations, an optional constructor, and one or more exported functions. User-submitted contracts must have names starting with con_, and all deployed contract names must use lowercase ASCII letters, digits, and underscores only.
E
Export
The @export decorator marks a function as publicly callable -- by user transactions or by other contracts. All arguments must have type annotations.
H
Hash
A key-value mapping that persists on-chain. Supports up to 16 key dimensions. Declared with Hash() or Hash(default_value=0).
M
Metering
The system that charges contract execution work. Xian supports tracer-backed Python execution and a native VM gas schedule. Both prevent infinite loops and ensure deterministic chi accounting.
N
Nonce
A sequential counter for each address. Each transaction from an address must have the next expected nonce. Prevents replay attacks (submitting the same transaction twice).
O
ORM
Object-Relational Mapping. In Xian, refers to the Variable, Hash, ForeignVariable, and ForeignHash classes that provide a Pythonic interface to on-chain storage.
S
Signer
The original signer of a transaction, available as ctx.signer. This value never changes in a call chain -- even when contract A calls contract B, ctx.signer remains the address of the user who submitted the transaction.
Chi
Xian's name for transaction execution energy and the unit of computation cost on the network, analogous to gas on Ethereum. Chi is not a separate token or an acronym. Every operation (instruction execution, storage read, storage write) costs chi. Chi are purchased with XIAN at a rate of 20 chi per XIAN.
T
XIAN
The native currency of the Xian network. Used to pay for chi (transaction fees), for transfers between addresses, and for staking.
Transaction
A signed message that instructs the network to execute a contract function with specific arguments. Contains the contract name, function name, keyword arguments, chi limit, chain ID, nonce, and signature.
V
Validator
A node that participates in consensus. Validators propose blocks, vote on block validity, and execute transactions. Validators must stake XIAN and run the same software version.
Variable
A single-value storage primitive that persists on-chain. Declared with Variable() or Variable(default_value=0). Use .set(value) and .get() to write and read.