XChain's design follows from one principle and six corollaries. The principle is verify, don't re-execute: an upper layer confirms a proof that a lower layer did its work correctly, rather than re-running it. This is what makes planetary scale thinkable.

Above every design choice sits one commitment: XChain is a public good, built, run and owned by its community — its direction, strategy, technology and even this whitepaper are open to contribution and, over time, to community governance; no founding team fixes them (see Governance & Community).

#	Principle	What it means
1	Aggregate, not global	Large capacity is aggregate nominal throughput, never one synchronous global state.
2	Locality-first	Over 99% of activity should stay local; placing state correctly is job one.
3	Assurance ∝ value	A transaction's security, data availability and proof scale with what it is worth.
4	Verify, don't re-execute	The layer above checks an aggregated proof instead of re-running the work.
5	A narrow waist	The core stays small and hard-defined; the space to build above it is unbounded.
6	Prune by default	Low-value data expires; only the commitment is permanent; every chain pays its own way.

What the core refuses to do. The principles are easiest to grasp through their prohibitions, because they let a reader predict where any function belongs. The root of trust refuses to execute anyone's transactions — it only verifies and finalizes proofs. The data Domain refuses to hold value — and refuses per-record consensus, because a tamper-evident log does not need it. The narrow waist refuses to grow — anything that can live above the core must live above the core. And no Tier refuses to forget: low-value data expires on schedule, leaving only its commitment behind. Whenever a feature is proposed, these refusals answer the placement question before any debate starts.

Diagram

Figure 2 — The placement law: what the core refuses to do already decides where anything belongs.

Takeaway: every corollary serves one goal — let most of the world's volume travel a near-free path, while value and atomicity concentrate in the small, most-protected core. Scale and safety stop fighting each other. The next section shows the structure these rules force: two Domains, three Layers, five Tiers — one system, described at three resolutions.