Ontology API

Strategos.Ontology is a type-safe semantic graph for domain modelling: Object Types, Properties, Links, Actions, Events, Lifecycles, and Interfaces declared in C# and validated at compile time by Roslyn source generators. Agents and dispatchers query the composed graph at runtime through IOntologyQuery. This section documents the public API surface for each package — for task-oriented walkthroughs see the Ontology guide.

Package map

Package	Contains	Use when
LevelUp.Strategos.Ontology	DomainOntology, fluent builders (IOntologyBuilder, IObjectTypeBuilder<T>, …), descriptor records, IOntologyQuery, IObjectSetProvider, IObjectSetWriter, expression nodes, IActionDispatcher, IEmbeddingProvider, IOntologySource, OntologyGraph	You define domain ontologies or write a runtime consumer (e.g. an MCP tool, a dispatcher decorator).
LevelUp.Strategos.Ontology.Generators	Roslyn incremental generator emitting validation diagnostics (AONT001–AONT208) and the source-generated IOntologyQuery implementation.	Always — referenced as an Analyzer by the core package’s consumers.
LevelUp.Strategos.Ontology.Npgsql	PgVectorObjectSetProvider, PgVectorOptions, schema-creation helpers. Implements IObjectSetProvider + IObjectSetWriter against PostgreSQL with the pgvector extension.	You run similarity search against a PostgreSQL instance with pgvector.
LevelUp.Strategos.Ontology.Embeddings	OpenAI-compatible IEmbeddingProvider implementation.	You need a production embedding provider without writing your own.
LevelUp.Strategos.Ontology.MCP	Progressive disclosure MCP integration (OntologyToolDescriptor, _meta envelope).	You expose ontology actions over MCP.

Reference pages

The pages below are sourced directly from the .cs files under src/Strategos.Ontology/ and src/Strategos.Ontology.Npgsql/. Each page lists members with signatures, return types, and the XML-doc summary attached to the member.

• IOntologyQuery — runtime query surface (types, actions, links, lifecycle, blast radius, pattern violations).
• IObjectSetProvider & expressions — read/write paths against an object backend and the expression tree they consume.
• IEmbeddingProvider — embedding generation contract.
• Action Dispatcher — IActionDispatcher, DispatchReadOnlyAsync, ActionResult, IActionDispatchObserver.
• IOntologySource & Builder — external-source extension contract and the IOntologyBuilder DSL.
• Graph Versioning — OntologyGraph.Version hash and cache invalidation.
• Strategos.Ontology.Npgsql — pgvector-backed provider, PgVectorOptions, EnsureSchemaAsync.

For the broader architectural picture (Palantir concept mapping, source-generator pipeline, agent query interface), see Platform Architecture §4.14.

Where to go from here

• Building your first ontology: start with Getting Started with Ontology.
• Similarity search setup: Similarity search guide walks through IEmbeddingProvider + pgvector end to end.
• Diagnostic code lookup: Diagnostics index lists every AONT code with severity and fix.