Terminology

This page defines protocol terms used throughout the App Layer specification. Each term is defined once, and other pages in this section use these terms consistently.

Naming Conventions

• Protocol entities use CamelCase, for example ChannelState and AppSession.
• Field names use CamelCase, for example ChannelId and StateVersion.
• Operations use lowercase with hyphens in document references, for example state-advancement.

Core Entities

Term	Definition
Channel	A state container shared between a User and a Node that allows off-chain state updates while maintaining on-chain security guarantees. Each channel operates on a single unified asset.
Channel Definition	The immutable parameters that define a channel: User, Node, asset, nonce, challenge duration, and approved signature validators. A channel definition is fixed at creation time and MUST NOT change during the channel lifecycle.
Channel State	The current agreed configuration of a channel, including home and non-home ledger allocations, a version number, and a transition field.
Participant	An entity that holds a signing key and participates in a channel. Each channel has exactly two participants: a User and a Node.
Asset	A representation of value identified by a human-readable symbol and decimal precision. Assets are identified independently of any specific blockchain.

State Concepts

Term	Definition
State	An abstract data structure representing the current configuration of a protocol entity at a specific version.
State Version	A monotonically increasing integer that identifies the order of state updates. During off-chain advancement, each new state MUST have a version exactly one greater than the previous state.
State Advancement	The process of updating a protocol entity's state off-chain through signed transitions exchanged between participants.
State Enforcement	The process of submitting a signed state to the blockchain layer for on-chain validation and enforcement.
Transition	A typed operation that describes the reason and parameters for a state update. Each transition carries a type, transaction identifier, account identifier, and amount.
Intent	A value derived from the transition type that determines how the blockchain layer processes an enforced state.

Cryptographic Concepts

Term	Definition
Signature	A cryptographic proof that a specific key holder authorized a specific message. The protocol uses ECDSA over secp256k1.
Signer	An entity capable of producing signatures. Each signer is associated with a specific key.
Session Key	A delegated signing key authorized by a participant's primary key to sign state updates on their behalf within an authorization scope.
Signature Validation Mode	A mechanism that determines how a signature is verified. The protocol currently defines default mode (0x00) and session key mode (0x01).

:::warning Session key authority Session key authorization MUST be associated with the same address as the channel's User or Node participant. Participants SHOULD treat session-key compromise as equivalent to control of the participant's authority within the scope they issued, for the duration of the validity window. :::

Ledger Concepts

Term	Definition
Ledger	A record of asset allocations within a channel, associated with a specific blockchain. Each ledger tracks User and Node allocations and net flows, and MUST satisfy the allocation/net-flow invariant.
Home Ledger	The primary ledger of a channel state, associated with the blockchain where the state is enforced.
Non-Home Ledger	A secondary ledger tracking asset allocations on a blockchain other than the home chain. Used for cross-chain escrow operations and migrations.
Home Chain	The blockchain identified by the home ledger's chain identifier. The home chain determines where enforcement operations are executed and MAY change through migration.
Locked Funds	The total assets held by the blockchain enforcement contract on behalf of a channel. Unless the channel is being closed, UserAllocation + NodeAllocation MUST equal the locked funds.
Vault	A pool of available funds maintained by the Node on a specific blockchain, separate from any specific channel.
WAD Normalization	Scaling chain-specific asset amounts to the asset's configured decimal precision for exact, lossless cross-chain comparisons.

WAD normalization is:

NormalizedAmount = Amount * 10^(18 - ChainDecimals)

Each unified asset defines a canonical decimal precision used during protocol interactions. The maximum supported decimal precision is 18.

State Signing Categories

Term	Definition
Mutually Signed State	A state that carries valid signatures from both the User and the Node. Only mutually signed states are enforceable on-chain.
Node-Issued Pending State	A state produced by the Node that carries only the Node's signature. A pending state is NOT enforceable on-chain and becomes mutually signed only after the User acknowledges it.
Channel Status	A specific on-chain channel data configuration throughout the lifecycle. The current RPC status surface is void, open, challenged, closing, and closed; closing means the Node has issued the finalization state and the channel is in the close path.
Escrow Channel Identifier	A 32-byte hash derived deterministically from the home channel identifier and state version. It uniquely identifies each escrow operation.

Protocol Operations

Operation	Definition
State Enforcement	Submitting a signed state to the blockchain layer so the latest agreed state is recorded on-chain. SDK or contract surfaces may expose a narrower checkpoint entry point for specific enforcement paths.
Challenge	An on-chain operation where a participant disputes the current enforced state by submitting a signed state and challenger signature.
Commit	Moving assets from a channel into an extension, such as an application session.
Release	Returning assets from an extension back to channel allocations.
Escrow	A two-phase mechanism for cross-chain operations: initiate locks funds, finalize releases them upon cooperative completion or after a timeout.

Extension Concepts

Term	Definition
Extension	An additional protocol module that provides functionality beyond the core channel protocol.
Application Session	An extension that enables off-chain application functionality. Application sessions hold committed assets and maintain their own state.
Application State	The state associated with an application session, tracking committed assets and application-specific data.