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Statement Store

Introduction

The Statement Store method group lets a Product publish and subscribe to signed, gossip-distributed statements on the People Chain. The Statement Store itself, including the pallet, gossip layer, lifecycle, and validation rules, is a network-layer pub/sub primitive. It is short-lived, allowance-gated, and propagated peer-to-peer. This TrUAPI group is how a Product reaches it through the Host.

The Product SDK wraps this surface as StatementStoreClient from @parity/product-sdk-statement-store. For the conceptual model of what statements are good for (versus the Bulletin Chain or local storage), see Where to Store Data.

Conceptual Contract

The group exposes the standard pub/sub surface with the Host filling in the parts a Product cannot do safely on its own:

  • Publishing a statement: The Product hands the Host a payload (under the per-statement 512-byte limit), a topic, a channel, a time to live (TTL), and any options. The Host requests an authentication proof from the paired App, attaches the per-Product account context and primary topic (blake2b(appName)), and submits to the People Chain node's statement_submit JSON-RPC.
  • Subscribing to a topic filter: The Product registers a callback for statements matching its primary topic plus any secondary topic2. The Host opens the underlying statement_subscribeStatement JSON-RPC, decodes payloads, and deduplicates by content hash before invoking the callback.
  • Channel-based last-write-wins: When a statement carries a channel, the pallet replaces older statements from the same account on the same channel. The SDK abstracts this as ChannelStore<T> on top of the underlying method group.

Delivery is best-effort gossip, with no retry, acknowledgment, or ordering guarantee. Reliability is composed at the application layer. For example, if a recipient needs to confirm receipt, they publish an acknowledgment statement back.

For the Desktop-side mediation perspective, see Statement Store via Host API.

Provisional

Detailed error taxonomy, allowance-management primitives, and any direct topic-walking API remain provisional.

Where to Go Next

  • Guide Exchange Ephemeral Messages

    The Product-side how-to: setting up the client, subscribing, publishing typed statements, and using channels.

    Get Started

  • Learn Statement Store via Host API

    What Polkadot Desktop adds when mediating Statement Store traffic, including proof routing, account context, and per-Product topic scoping.

    Reference

Last update: September 22, 2026
| Created: June 16, 2026