Storage Encoding

Storage encoding is deterministic and sparse.

Descriptor

The compiler emits a StorageLayoutDescriptor.

It includes:

• field name;
• type;
• default;
• canonical storage path.

The descriptor is compiler output. It defines how storage is named and compared across versions.

Sparse Persistence

Ledger storage is keyed by:

• contract id;
• namespace;
• path hash.

Sparse maps and vectors persist only non-default entries.

This means:

• default values do not need physical storage rows;
• deleting back to default removes sparse entries;
• large sparse structures remain compact when most values are unset.

Compatibility

Layout compatibility can be classified as:

• identical;
• append-only;
• incompatible.

Automatic incompatible migration execution is outside the current closed profile.

Step-By-Step Model

1. the compiler emits a storage layout descriptor;
2. the contract instance uses that layout to interpret persisted storage;
3. accepted version changes are checked against storage compatibility;
4. incompatible layouts are rejected from the current executable upgrade path.