Sage Ontology

Ontology

Typed knowledge graph. Entities stored as memories, relationships stored as edges — searchable, traversable, persistent.

Part of the unified knowledge system. Ontology entries surface alongside regular knowledge and self-learning entries during recall.

Capabilities by Backend

How to detect backend: At session start, call sage_memory_set_project with the project root path. If it responds, use MCP. If not, use .sage-memory/ files.

Agent-driven extraction (0.9+). Ontology entities are populated primarily by passing entities and relations to sage_memory_store from the calling agent:

sage_memory_store(
  content: "...",
  entities: [{name: "PaymentOrchestrator", type: "CONCEPT"}],
  relations: [{from: "PaymentOrchestrator", to: "Stripe", rel: "depends_on"}]
)

The background worker is a fallback that runs only when an LLM API key is configured AND the agent didn't pass an extraction payload. Prefer the agent-driven path: your model has the full conversational context, the worker only sees the stored content.

Core Model

Entities hold properties. Relations connect two entities with a typed, directed edge.

Entity:   [Task:task_a1b2] "Fix payment timeout"
Relation: task_a1b2 —blocks→ task_f3a4

Entity Operations

Create Entity

With MCP:

sage_memory_store(
  title: "[Task:task_a1b2] Fix payment timeout in checkout flow",
  content: '{"id":"task_a1b2","type":"Task","properties":{"title":"Fix payment timeout","status":"open","priority":"high"}}',
  tags: ["ontology", "entity", "task", "billing", "checkout"],
  scope: "project"
)

With files:

File: .sage-memory/ont-task-a1b2-fix-payment-timeout.md

---
tags: [ontology, entity, task, billing, checkout]
type: ontology
scope: project
entity_id: task_a1b2
entity_type: Task
created: 2026-03-20
---

{"id":"task_a1b2","type":"Task","properties":{"title":"Fix payment timeout","status":"open","priority":"high"}}

Filename convention: ont-{type}-{id}-{short-description}.md

ID format: {type_prefix}_{8_hex} — e.g., task_a1b2c3d4, pers_e5f6a7b8, proj_c9d0e1f2

Search Entities

With MCP:

sage_memory_search(query: "task_a1b2", filter_tags: ["ontology", "entity"])
sage_memory_search(query: "open tasks billing", filter_tags: ["ontology", "entity", "task"])

FTS5 safety: Search by bare entity ID, never by bracket title.

With files: Scan .sage-memory/ for ont- prefixed files. Filter by type: ont-task-* for tasks, ont-pers-* for persons. Read matching files to check properties.

Browse All Entities

With MCP: sage_memory_list(tags: ["ontology", "entity", "task"])

With files: List all ont-task-*.md files in .sage-memory/.

Delete Entity

With MCP: sage_memory_delete(id: "<entity_memory_id>") — CASCADE automatically removes all edges.

With files: Delete the entity file. Then scan other ont-*.md files for relations: entries referencing this entity's ID and remove them.

Relation Operations

Create Relation

With MCP:

sage_memory_link(
  source_id: "<source_memory_id>",
  target_id: "<target_memory_id>",
  relation: "blocks",
  properties: {"reason": "payment flow must complete first"}
)

One call. Validation before creating:

1. Check type compatibility (see schema reference)
2. Check cardinality (many_to_one → replace existing if found)
3. For blocks/depends_on → cycle check via sage_memory_graph

With files: Add a relations: section to the source entity's file:

File: .sage-memory/ont-task-a1b2-fix-payment-timeout.md

---
tags: [ontology, entity, task, billing, checkout]
type: ontology
scope: project
entity_id: task_a1b2
entity_type: Task
created: 2026-03-20
relations:
  - rel: blocks
    target: task_f3a4
    target_type: Task
  - rel: assigned_to
    target: pers_e5f6
    target_type: Person
---

{"id":"task_a1b2","type":"Task","properties":{"title":"Fix payment timeout","status":"open","priority":"high"}}

Relations live inside the source entity's frontmatter. This is denormalized but avoids separate relation files and works without a database. To find what blocks task_f3a4, scan all ont-task-*.md files for relations: entries with target: task_f3a4.

Delete Relation

With MCP:

sage_memory_link(
  source_id: "<source_id>", target_id: "<target_id>",
  relation: "blocks", delete: true
)

With files: Edit the source entity file — remove the relation entry from the relations: list.

Cycle Check

With MCP:

sage_memory_graph(
  id: "<target_memory_id>",
  relation: "blocks",
  direction: "outbound",
  depth: 5
)

If source_id appears in results → cycle → reject.

With files: Manually trace the chain. Read target's file → check its relations: for outbound blocks → follow to next entity → repeat. If you return to the source, it's a cycle. Practical for graphs under 20 edges of that type.

Graph Traversal (MCP only)

What tasks does project X have?

sage_memory_graph(id: "<project_id>", relation: "has_task", direction: "outbound", depth: 1)

What blocks task X, and what blocks those?

sage_memory_graph(id: "<task_id>", relation: "blocks", direction: "inbound", depth: 2)

Full neighborhood

sage_memory_graph(id: "<entity_id>", direction: "both", depth: 1)

With files: Multi-hop traversal is not available. Use single-hop lookups by scanning relations: in entity files. For tasks in a project, scan all ont-task-*.md files for relations: entries like {rel: part_of, target: <project_id>}.

Planning as Graph Transformation

Plan: "Set up feature project with tasks"

1. CREATE Project → sage_memory_store (or file)
2. CREATE Task1 → sage_memory_store (or file)
3. CREATE Task2 → sage_memory_store (or file)
4. RELATE has_task: Project → Task1 → sage_memory_link (or add to file)
5. RELATE has_task: Project → Task2 → sage_memory_link (or add to file)
6. RELATE blocks: Task1 → Task2 → sage_memory_link (after cycle check)
7. VALIDATE: no cycles ✓, cardinality ✓

Validating a planned mutation with graph_check.py

scripts/graph_check.py is a zero-dependency Python validator. Pipe it a JSON document describing the entities and proposed relations to get a structural OK / FAIL plus a list of violations. Use it before the agent calls sage_memory_link for a non-trivial plan.

python3 scripts/graph_check.py <<'EOF'
{
  "entities": [
    {"id": "proj_c9d0", "type": "Project"},
    {"id": "task_a1b2", "type": "Task"},
    {"id": "task_f3a4", "type": "Task"}
  ],
  "relations": [
    {"from": "proj_c9d0", "to": "task_a1b2", "rel": "has_task"},
    {"from": "proj_c9d0", "to": "task_f3a4", "rel": "has_task"},
    {"from": "task_a1b2", "to": "task_f3a4", "rel": "blocks"}
  ]
}
EOF

Exit code 0 = valid; 1 = violations (printed as JSON to stdout). Checks type compatibility, cardinality, and acyclicity for blocks and depends_on chains. See the script's docstring for the full input schema.

Validation Rules

Required Properties

Relation Types

The full controlled vocabulary lives in references/schema.md. All 11 built-in relations:

Custom relation strings are accepted by sage_memory_link but only the 11 above are validated by graph_check.py. Stick to the controlled vocabulary unless the project clearly needs an extension.

Credential safety: Never store password, secret, token, api_key as properties.

Extending Types

Store a schema extension for custom types (works with both backends):

With MCP:

sage_memory_store(
  title: "[Schema:Sprint] Custom entity type",
  content: '{"type":"Sprint","required":["name","start","end"]}',
  tags: ["ontology", "schema"]
)

With files:

File: .sage-memory/ont-schema-sprint.md

---
tags: [ontology, schema]
type: ontology
---

{"type":"Sprint","required":["name","start","end"],"enums":{"status":["planning","active","closed"]}}

Codebase Scan (0.11+)

For projects where code symbols (functions, classes, modules) are a recurring discovery target, sage-memory can pre-index the source tree via tree-sitter.

If sage-memory scan-codebase --help exits 0: the [codebase] extra is installed. Run sage-memory scan-codebase (default: project root) at session start or after notable code changes. Then use:

• sage_memory_search(query: "...", filter_tags: ["codebase"]) — surface files matching the query.
• sage_memory_scan_codebase(...) MCP tool — same as the CLI.

If the extra is NOT installed: the CLI / MCP tool errors with an install hint. Fall back to extracting code entities yourself via your existing AST tools and the 0.9.0 entities / relations payload on sage_memory_store.

The pre-indexed codebase saves 10-50× tokens on cross-file queries ("where is X called?", "what imports Y?", "what functions exist in this module?"). For line-level edits, you still need to read source.

10 languages supported: Python, TypeScript (incl. TSX), JavaScript (incl. JSX), Go, Rust, Java, Ruby, PHP, C, C++. Symbol kinds captured: FUNCTION, CLASS, METHOD, INTERFACE, STRUCT, ENUM. Relations captured: imports, calls — with confidence: resolved | unresolved so you can filter for high-signal cross-file links.

Safety guards (T10b): scans are project-scoped (different projects can scan in parallel), refuse to run against $HOME, respect --limit (default 5000) BEFORE writes happen, and hold a 600s-recovery advisory lock that prevents two scans from racing on the same project.

References

• references/encoding.md — Full format, examples, search patterns
• references/schema.md — All types, relations, constraints
• scripts/graph_check.py — Structural validator