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1. Introduction

What is AUSUS 2.0 (Entity Engine)?​

AUSUS is a metadata-first application engine. You describe an application as declarative metadata — entities, fields, actions, projections, and authorization rules — and AUSUS compiles that description into a content-addressed schema and executes it: it persists data, enforces data-aware authorization, exposes an HTTP API, and renders a generic React UI. You write what the application is; the engine runs it.

The 2.0 Entity Engine is the realization of two frozen RFCs:

  • EE-RFC-012 — Entity Definition: the declarative model (EntityDefinition = identity + tenant flag + Field[] + Action[] + Projection[], with an embedded authorization Expression).
  • EE-RFC-011 — Entity Engine: the execution contract (compile → EntitySchema; bind(EntitySchema, Driver) → RuntimeEntity with invoke/read).

Why does it exist?​

A typical enterprise application re-implements the same plumbing for every domain: storage mapping, per-record authorization, read shapes, transitions, and a UI. AUSUS factors that plumbing into a single engine so the application is expressed once, declaratively, and the cross-cutting concerns (tenancy, authorization, transactions) are properties of the engine rather than code each team must get right.

Principles (as implemented in 2.0)​

  • Metadata-first. The application is data (EntityDefinition), not code. The authored PHP DSL is a closed notation whose only product is an EntityDefinition.
  • Content-addressed compilation. A definition compiles to an EntitySchema addressed by a hash of its canonical (normalized) form. Same semantics ⇒ same hash. Re-running bind/read/invoke never recompiles.
  • Driver-agnostic runtime. RuntimeEntity depends only on the frozen PersistenceDriver/Repository contracts; the concrete driver is injected.
  • Data-aware, fail-closed authorization. Guards are predicates over facts (actor, tenant, now, subject, input); an unresolved fact denies.
  • Single rendering contract. The React renderer consumes only the HTTP API — it has no knowledge of the kernel, the compiler, or the repository.

What 2.0 is not​

It is not (in this slice) an ORM, a UI framework, a workflow engine, or a query language. Expand is single-hop; projections do not aggregate; read() selection parameters are deferred. See Known limits.