create-ontology

name	create-ontology
description	Build a business entity graph (ontology) from annotated sources and taxonomy. Use after annotate-sources to design the entity model before CDM generation.

Create ontology

Build a formal entity graph from the confirmed source annotations and taxonomy, ready for Kimball CDM design.

Requires .schema/<cdm-name>/<pipeline_name>.dbml (one per pipeline, annotated) and .schema/<cdm-name>/taxonomy.json from annotate-sources. If either is missing, run annotate-sources first.

Read _name from taxonomy.json to determine <cdm-name> — all files in this skill are under that folder.

Key concept: natural key

A natural key is a column whose value is derived from the real-world domain and is therefore consistent across multiple source systems. For example, email appearing in both contacts (AC) and event_guests (Luma) means a single person can be matched and merged across both sources.

When a concept has a natural key, rows from different source tables that share the same natural key value are treated as the same entity — they become one row in the CDM, not two. This determines:

• Which source "wins" for each attribute when both have a value (master source)
• Whether rows that exist in only one source are still included (union vs. intersection)

Steps

1. Build entity list

Read .schema/<cdm-name>/taxonomy.json. For each top-level key that is not prefixed with _ (i.e. not _version, _excluded):

• Create one ontology entity per canonical concept
• Name = concept key (PascalCase)
• Mark as inferred: false (grounded in confirmed source mappings)

2. Confirm natural key handling

Before deriving any attributes, for every concept that has a natural_key in taxonomy.json, explicitly ask the user how they want conflicts resolved. Do not assume a strategy.

Present the concept with its natural key, the contributing sources, and the three options:

Person appears in HubSpot (contacts) and Luma (event_guests), linked by email.

When the same person appears in both and their data conflicts, which should we trust?

  A) Prefer whichever source has a value — fall back to the other if blank
     → "Use HubSpot if available, fall back to Luma"
  B) Always use one source, ignore the other entirely
     → "Always use HubSpot, even if a field is blank"
  C) Decide field by field
     → "Use HubSpot for name/phone, Luma for registration date"

Also: what about people who only exist in one source?
  1) Include everyone (recommended)
  2) Only include people present in both sources

Which combination (A/B/C) and (1/2)?

Wait for explicit confirmation. Record the chosen strategy in the ontology assumption field before proceeding to attribute derivation.

3. Derive attributes per entity

SCOPE CONSTRAINT — no inference beyond source data: Only include attributes that correspond to actual columns in the source schema. Do not add computed fields, business metrics, or domain concepts (e.g. roi, is_icp, lead_score, lifetime_value) unless a column with that data already exists in one of the source tables. If a useful attribute is missing from the data, record it as a semantic gap (step 5), not as an attribute.

For each entity, collect all columns from all source tables mapped to that concept (from taxonomy[concept].tables).

For each column:

• Include column name, dlt type, source table, source pipeline
• Apply the confirmed natural key strategy from step 2 to flag the master source per attribute

Where the same logical attribute appears in multiple sources under different names (e.g. phone in contacts, phone_number in guests):

• Propose a canonical attribute name
• Present conflicts to the user and confirm:

Both sources have a phone field for Person, but named differently:
  HubSpot (contacts): phone
  Luma (guests): phone_number

Suggested unified name: phone  |  Primary source: HubSpot (contacts)
OK?

Wait for confirmation before proceeding.

4. Define relationships

Two sources of relationships:

From natural keys (taxonomy.json → concept.natural_key):

• Each natural key defines a union relationship between tables of the same concept
• Record as a STITCHED_BY edge with the key column

From structural FKs in source schemas (.schema/<cdm-name>/<pipeline_name>.dbml):

• Identify foreign key columns (e.g. company_id on contacts → Company entity)
• Map to inter-entity relationships
• Use UPPER_SNAKE_CASE edge labels (e.g. BELONGS_TO, ATTENDED, PLACED_BY)

5. Flag semantic gaps

Compare entity list against the user's stated use cases (from taxonomy.json → concept.use_cases).

If a use case requires a concept that has no contributing source table:

• Flag it as a semantic gap
• Record it as an assumption: {"gap": "Contract entity needed for billing use case, no source table found"}
• Suggest where this data might come from (new pipeline, manual input, derivable from existing tables)

Present gaps to the user before writing output.

6. Write ontology

Write .schema/<cdm-name>/ontology.ison in Graph ISON format (https://graph.ison.dev/) — tabular DSV sections, NOT JSON:

nodes.Entity
id       label    inferred  assumption
Person   Person   false     Collapses hubspot contact + luma guest. Natural key: email.
Company  Company  false     Master source: hubspot__companies.

nodes.Attribute
entity           name        type       master_source          also_in          note
:Entity:Person   email       text       hubspot__contacts      luma__guests     natural_key
:Entity:Person   first_name  text       hubspot__contacts

edges.BELONGS_TO
from              to               via                                        inferred
:Entity:Person    :Entity:Company  hubspot__contacts.associated_company_id   false

edges.STITCHED_BY
from            to              via    inferred
:Entity:Person  :Entity:Person  email  false

Rules:

• One nodes.<Type> section per entity type; one edges.<LABEL> section per relationship label
• Node references use :Type:id syntax (e.g. :Entity:Person)
• Attributes are a separate nodes.Attribute section with an entity reference column
• Tab-separate columns; use a blank line between sections

If semantic gaps were found in step 5, append:

nodes.SemanticGap
concept   use_case                       note
Contract  track subscription billing     no source table found

Output

• .schema/<cdm-name>/ontology.ison — entity graph with attributes, relationships, and gaps
• .schema/<cdm-name>/ontology.md — human-readable summary (required). One section per entity with: a short description, attribute table (name | type | source | notes), relationships table, and a final assumptions & exclusions list.

After writing both files, explicitly ask the user to open and review .schema/<cdm-name>/ontology.md before continuing:

Please review `.schema/<cdm-name>/ontology.md` — it summarises every entity, its attributes, and the relationships between them.

Let me know if anything looks wrong or needs changing before we move on.

Wait for explicit confirmation before handing over to generate-cdm skill.