Module polkadot_sdk_docs::reference_docs::glossary

The glossary.

Glossary

State

The data around which the blockchain network wishes to come to consensus. Also referred to as “onchain data”, “onchain storage” or sometimes just “storage”. In UTXO based blockchains, is referred to as “ledger”.

Synonyms: Onchain data, Onchain storage, Storage, Ledger

State Transition Function

The WASM Blob that dictates how the blockchain should transition its state upon encountering new blocks.

Host

The environment that hosts and executes the state transition function’s WASM blob.

Node

The full software artifact that contains the host, but importantly also all the other modules needed to be part of a blockchain network, such as peer-to-peer networking, database and such.

Synonyms: Client

Light Node

Same as node, but when capable of following the network only through listening to block headers. Usually capable of running in more constrained environments, such as an embedded device, phone, or a web browser.

Synonyms: Light Client

Offchain

Refers to operations conducted outside the blockchain’s consensus mechanism. They are essential for enhancing scalability and efficiency, enabling activities like data fetching and computation without bloating the blockchain state.

Host Functions:

Host functions are the node’s API, these are functions provided by the runtime environment (the host) to the Wasm runtime. These functions allow the Wasm code to interact with and perform operations on the node, like accessing the blockchain state.

Runtime API:

This is the API of the runtime, it acts as a communication bridge between the runtime and the node, serving as the exposed interface that facilitates their interactions.

Dispatchable:

Dispatchables are function objects that act as the entry points in FRAME pallets. They can be called by internal or external entities to interact with the blockchain’s state. They are a core aspect of the runtime logic, handling transactions and other state-changing operations.

Synonyms: Callable

Extrinsic

An extrinsic is a general term for a piece of data that is originated outside of the runtime, included into a block and leads to some action. This includes user-initiated transactions as well as inherents which are placed into the block by the block-builder.

Pallet

Similar to software modules in traditional programming, FRAME pallets in Substrate are modular components that encapsulate distinct functionalities or business logic. Just as libraries or modules are used to build and extend the capabilities of a software application, pallets are the foundational building blocks for constructing a blockchain’s runtime with frame. They enable the creation of customizable and upgradeable networks, offering a composable framework for a Substrate-based blockchain. Each pallet can be thought of as a plug-and-play module, enhancing the blockchain’s functionality in a cohesive and integrated manner.

Full Node

It is a node that prunes historical states, keeping only recent finalized block states to reduce storage needs. Full nodes provide current chain state access and allow direct submission and validation of extrinsics, maintaining network decentralization.

Archive Node

An archive node is a specialized node that maintains a complete history of all block states and transactions. Unlike a full node, it does not prune historical data, ensuring full access to the entire blockchain history. This makes it essential for detailed blockchain analysis and historical queries, but requires significantly more storage capacity.

Validator

A validator is a node that participates in the consensus mechanism of the network. Its role includes block production, transaction validation, network integrity and security maintenance.

Collator

A collator is a node that is responsible for producing candidate blocks for the validators. Collators are similar to validators on any other blockchain but, they do not need to provide security guarantees as the Relay Chain handles this.

Parachain

Short for “parallelized chain” a parachain is a specialized blockchain that runs in parallel to the Relay Chain (Polkadot, Kusama, etc.), benefiting from the shared security and interoperability features of it.

Synonyms: AppChain

PVF

The Parachain Validation Function (PVF) is the current runtime Wasm for a parachain that is stored on the Relay chain. It is an essential component in the Polkadot ecosystem, encapsulating the validation logic for each parachain. The PVF is executed by validators to verify the correctness of parachain blocks. This is critical for ensuring that each block follows the logic set by its respective parachain, thus maintaining the integrity and security of the entire network.

Synonyms: Parachain Validation Function