BAC-L2-DOT-107Polkadot
XCM: foundations of the cross-chain message
XCM is not a transport protocol but an instruction language. That distinction is the source of most design mistakes.
- Level
- L2 — Appchain developer
- Duration
- 4 h
- Track
- Polkadot
- Maintainer
- Polkadot / Substrate Lead Architect
Learning objectives
- 01Read and write an XCM message instruction by instruction
- 02Separate the message format from its transport channel
- 03Interpret a remote execution failure
Guided lab
Compose and execute a simple XCM message between two chains on a local network.
Independent lab
Trigger three distinct XCM failures and document the exact cause of each.
Security angle
Origins and barrier filtering: why accepting a message from an unknown chain is a security decision.
Assessment
Annotated failure log, marked on diagnostic precision.