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Truth Source: Repository schemas and tests are authoritative.

PSG - Project Semantic Graph

Status: Draft runtime concept page
Authority: Non-authoritative documentation surface
Boundary: PSG is described here as a runtime concept and logical state model. This page does not define a mandated physical implementation.

1. Purpose​

PSG, or Project Semantic Graph, is the logical runtime model used to organize MPLP protocol objects and their relations.

In practical terms, runtimes may use PSG to represent:

  • protocol objects such as Context, Plan, Confirm, Trace, Role, Collab, Dialog, Extension, and Network
  • relations between those objects
  • the runtime's current view of project state

2. Boundary​

This page does not claim that MPLP mandates:

  • one specific graph database
  • one specific in-memory graph engine
  • one specific node/edge implementation
  • one universal runtime graph library

PSG is best understood as a logical state model / runtime contract concept, not as a single required storage product.

3. Relation to Protocol Truth​

Repository-backed schemas remain the truth source for protocol object structure.

PSG sits one layer lower in runtime realization:

  • schemas define what the objects are
  • runtimes decide how those objects are represented and related internally
  • PSG is a common way to talk about that internal logical representation

4. Typical Runtime Role​

Runtimes commonly use PSG-like structures to:

  • track object identity and linkage
  • reconcile state across modules
  • support traceability and drift detection
  • support state snapshots or state reconstruction

Those are runtime responsibilities, not standalone protocol objects.

5. Common Mapping Examples​

Typical logical mappings include:

  • Context as a root scope node
  • Plan as a node linked to its Context
  • Trace as a node linked to Context and optionally Plan
  • Confirm as a node linked to its target object
  • Collab as a node representing collaboration session state

This page intentionally avoids defining one canonical node taxonomy beyond those schema-grounded associations.

6. Relation to VSL​

PSG and VSL should not be collapsed into one concept.

  • PSG: logical state model / semantic runtime view
  • VSL: persistence abstraction used by a runtime

A runtime may implement PSG on top of VSL, but the protocol does not require one physical pattern for doing so.

7. References​

Final Boundary: PSG is a runtime-facing logical state model. It is not a separate L0 schema object and not a mandated physical storage implementation.