Glossary

This glossary defines Hyperledger Sawtooth terms and concepts.

Batch

Group of related transactions. In Sawtooth, a batch is the atomic unit of state change for the blockchain. A batch can contain one or more transactions. For a batch with multiple transactions, if one transaction fails, all transactions in that batch fail. (The client application is responsible for handling failure appropriately.) For more information, see Transactions and Batches.

Blockchain

Distributed ledger that records transactions, in chronological order, shared by all participants in a Sawtooth network. Each block on the blockchain is linked by a cryptographic hash to the previous block.

Consensus

Process of reaching agreement among a group of participants (nodes on a Sawtooth network), some of which could be faulty or malicious. Sawtooth supports many types of consensus algorithms with the Dynamic consensus feature.

Consensus API

Interface that allows a consensus engine to interact with the validator in order to handle consensus functionality in a separate process.

Consensus engine

Sawtooth component that provides consensus-specific functionality for a Sawtooth node. The consensus engine runs as a separate process on the node and communicates with the validator through the consensus API.

Core

See Sawtooth core.

Devmode consensus

(Formerly “dev mode consensus”.) Simple random-leader consensus algorithm that can be used to test a transaction processor on a single Sawtooth node. (Devmode is short for “developer mode”.) Devmode consensus is not recommended for a multiple-node network; it should not be used for production.

Distributed ledger

See Blockchain.

Dynamic consensus

Sawtooth feature that allows a variety of consensus algorithms (formerly called “pluggable consensus”). Dynamic consensus allows each Sawtooth network to choose the best consensus for its purposes, as specified by on-chain settings in the genesis block. Sawtooth supports the ability to change the consensus algorithm on a running network by submitting a transaction. For more information, see Dynamic Consensus.

Genesis block

First block on the blockchain. The genesis block initializes the Sawtooth network.

Global state

Database that stores a local (validator-specific) record of transactions for the blockchain. Sawtooth represents state in a single instance of a Merkle-Radix tree on each Sawtooth node. For more information, see Global State.

Identity

Sample transaction family that handles on-chain permissions (settings stored on the blockchain) for transactor and validator keys. This transaction family demonstrates how to streamline managing identities for lists of public keys. For more information, see Identity Transaction Family.

IntegerKey

Sample transaction family with only three operations (set, increment, and decrement) that can be used to test deployed ledgers. IntegerKey is called intkey. For more information, see IntegerKey Transaction Family.

Journal

Group of Sawtooth core processes that are responsible for maintaining and extending the blockchain for the validator. For more information, see Journal.

Merkle-Radix tree

Addressable data structure that stores state data. A Merkle-Radix tree combines the benefits of a Merkle tree (also called a “hash tree”), which stores successive node hashes from leaf-to-root upon any changes to the tree, and a Radix tree, which has addresses that uniquely identify the paths to leaf nodes where information is stored. For more information, see Merkle-Radix Tree Overview.

Node

Participant in Sawtooth network. Each node runs a single validator, a REST API, a consensus engine, and one or more transaction processors.

Off-chain setting

Setting or value that is stored locally, rather than on the blockchain.

On-chain setting

Setting or value that is stored on the blockchain (also referred to as “in state”) so that all participants on the network can access that information.

PBFT consensus

Practical Byzantine Fault Tolerance, a voting-based consensus algorithm with Byzantine fault tolerance (BFT) that has finality (does not fork). Sawtooth PBFT extends the original PBFT algorithm with features such as dynamic network membership, regular view changes, and a block catch-up procedure.

Permissioned network

Restricted network of Sawtooth nodes. A permissioned network typically includes multiple parties with a mutual interest but without the mutual trust found in a network controlled by a single company or entity.

The blockchain stores the settings that specify permissions, such as roles and identities, so that all participants in the network can access this information.

PoET consensus

Proof of Elapsed Time, a Nakamoto-style consensus algorithm that is designed to support large networks. PoET does not have finality (can fork).

Sawtooth offers two version of PoET consensus:

  • PoET-SGX relies on a Trusted Execution Environment (TEE), such as Intel® Software Guard Extensions (SGX), to implement a leader-election lottery system. PoET-SGX is sometimes called PoET/BFT because it is Byzantine fault tolerant.

  • PoET simulator provides the same consensus algorithm on a system without a Trusted Execution Environment. PoET simulator is also called PoET/CFT because it is crash fault tolerant, not Byzantine fault tolerant.

Raft consensus

Leader-based consensus algorithm that is designed for small networks with a restricted membership. Raft is crash fault tolerant, not Byzantine fault tolerant, and has finality (does not fork). For more information, see Raft (computer science) on Wikipedia and the Sawtooth Raft documentation.

REST API

In Sawtooth, a core component that adapts communication with a validator to HTTP/JSON standards. Sawtooth includes a REST API that is used by clients such as the Sawtooth CLI commands. Developers can use this REST API or develop custom APIs for client-validator communication. For more information, see REST API.

Sawtooth core

Central Sawtooth software that is responsible for message handling, block validation and publishing, consensus, and global state management. The Sawtooth architecture separates these core functions from application-specific business logic, which is is handled by transaction families.

Sawtooth network

Peer-to-peer network of nodes running a validator (and associated components) that are working on the same blockchain.

Settings

Sample transaction family that provides a reference implementation for storing on-chain configuration settings. For more information, see Settings Transaction Family.

State

See Global state.

State delta

Result of a single change for a specific address in global state.

State delta subscriber

Client framework that subscribes to a validator for state deltas (changes) for a specific set of transaction families. Usually, an application subscribes to state deltas for the purpose of off-chain storage or action, such as handling the failure of a transaction appropriately.

Transaction

Function that changes the state of the blockchain. Each transaction is put into a Batch, either alone or with other related transactions, then sent to the validator for processing. For more information, see Transactions and Batches.

Transaction family

Application-specific business logic that defines a set of operations or transaction types that are allowed on the blockchain. Sawtooth transaction families separate the transaction rules and content from the Sawtooth core functionality.

A transaction family implements a data model and transaction language for an application. Sawtooth includes example transaction families in several languages, such as Python, Go, and Java. For more information, see Sample Transaction Families.

Transaction processor

Validates transactions and updates state based on the rules defined by the associated transaction family. Sawtooth includes transaction processors for the sample transaction families, such as identity-tp for the Identity transaction family. For more information, see Transaction Family Specifications.

Validator

Component responsible for validating batches of transactions, combining them into blocks, maintaining consensus with the Sawtooth network, and coordinating communication between clients, transaction processors, and other validators on the network.

Validator node

See node.

XO

Sample transaction family that demonstrates basic transactions by playing tic-tac-toe on the blockchain. For more information, see XO Transaction Family.