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

Capability	MCP	Files
Create entities	✅ sage_memory_store	✅ .sage-memory/ont-*.md files
Search entities	✅ BM25 + tag filter	⚠️ filename scan + read
Update entities	✅ sage_memory_update	✅ edit file
Delete entities	✅ CASCADE removes edges	✅ delete file + clean relations
Create relations	✅ sage_memory_link	✅ relations: in entity file
Multi-hop traversal	✅ sage_memory_graph	❌ not available
Cycle detection	✅ built into graph tool	⚠️ manual trace
Browse by type	✅ sage_memory_list	✅ scan ont- files

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

Type	Required
Task	title, status
Person	name
Project	name
Event	title, start
Document	title

Relation Types

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

Relation	From → To	Cardinality	Acyclic
has_owner	Project, Task → Person	many_to_one	no
assigned_to	Task → Person	many_to_one	no
has_task	Project → Task	one_to_many	no
has_goal	Project → Goal	one_to_many	no
part_of	Task, Document, Event → Project	many_to_one	no
blocks	Task → Task	many_to_many	yes
depends_on	Task, Project → Task, Project, Event	many_to_many	yes
member_of	Person → Organization	many_to_many	no
mentions	Document, Message, Note → Person, Project, Task, Event	many_to_many	no
follows_up	Task, Event → Event, Message	many_to_one	no
attendee_of	Person → Event	many_to_many	no

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"]}}

References

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