VSL - Value State Layer

Status: Draft runtime concept page
Authority: Non-authoritative documentation surface
Boundary: This page describes VSL as a runtime persistence abstraction. It does not define a protocol object or mandate one storage architecture.

1. Purpose

VSL, or Value State Layer, is the persistence abstraction used by a runtime to store and retrieve state.

Typical runtime uses include:

persisting runtime state snapshots
persisting event-related state
supporting restore/recovery paths
backing higher-level logical models such as PSG

2. Boundary

This page does not define:

one mandatory VSL interface for all runtimes
one required backend such as Redis, Postgres, filesystem, or object store
one required transaction model
one required snapshot format

3. Relation to PSG

PSG and VSL are related but distinct:

PSG is the logical state model
VSL is the persistence/storage abstraction a runtime may use underneath

This page does not claim that VSL itself carries protocol semantics. Those semantics remain in schema, invariants, and runtime logic.

4. Minimal Runtime Artifact Surface

The current published runtime package includes a minimal InMemoryVSL artifact surface in @mplp/runtime-minimal.

That package artifact is useful for tests and examples, but it should not be misread as the only valid VSL design for MPLP.

5. Implementation Reading

The safest reading of VSL in MPLP is:

a runtime persistence abstraction
potentially used for snapshots, event accumulation, or state restoration
not itself a protocol truth source
not itself the semantic layer

6. References

Final Boundary: VSL is a runtime persistence concept. It is not a standalone protocol object and not a mandated storage implementation.

1. Purpose​

2. Boundary​

3. Relation to PSG​

4. Minimal Runtime Artifact Surface​

5. Implementation Reading​

6. References​