Phase 2: Structural Modeling & Taxonomy Design

You are designing the target-state taxonomy. The phase-1-landscape-report.md describes what exists today; your job is to define the conceptual structure the substrate will inhabit going forward — the categories, the attributes every item must carry, the relationships items have to each other, and who is allowed to see or modify what.

Preconditions

• <working-dir>/substrate-context.md exists.
• <working-dir>/phase-1-landscape-report.md exists and has passed gate 1 (PASS or PARTIAL-with-user-approval).
• Read both files in full before starting.

If phase 1 has not been audited yet, ask the user whether to invoke the structural-integrity-auditor agent first.

Four work streams

Stream 1 — Classify Entities

Group similar elements from the assets inventory into logical, universally understood categories.

For each entity class, define:

• Class name — singular noun that captures the essence (e.g., "Document", "Ticket", "Asset", "Component"). Use the substrate's own vocabulary where possible.
• Definition — one sentence stating what membership requires
• Examples from inventory — 2–4 specific assets from phase 1 that belong in this class
• Boundary cases — assets that almost fit but don't (and where they go instead)
• Estimated population — rough count of how many instances exist today

Aim for 5–15 classes. Fewer means under-classified (blob categories that won't help). More means over-classified (categories that will collapse together in practice).

Stream 2 — Standardize Attributes

Define the mandatory traits, labels, and metadata every item must carry, per entity class.

For each entity class, list:

Distinguish:

• Universal attributes that apply to ALL entity classes (id, created_at, owner — common cross-class metadata)
• Class-specific attributes that apply only to one class

Universal attributes go in a shared "Universal Schema" section; class-specific attributes go under each class.

Stream 3 — Establish Relationships

Map out how entity classes connect, depend on, and interact with each other.

For each relationship:

• From class → To class
• Cardinality — 1:1, 1:N, N:1, N:N
• Name — verb phrase describing the relationship from the From-class's perspective (e.g., "owns", "references", "supersedes", "blocks")
• Direction — directed (one-way) or symmetric (two-way)
• Lifecycle coupling — what happens to the To-class instance when the From-class instance is deleted/archived (cascade, restrict, set-null, no-op)

Optionally include a textual or ASCII relationship diagram showing the entity classes as nodes and relationships as edges.

Stream 4 — Design Access Framework

Determine visibility, ownership levels, and modification rights across tiers.

For each entity class, declare:

• Visibility tiers — who can see instances (e.g., public / org-wide / team / owner-only)
• Modification tiers — who can modify instances (often more restricted than visibility)
• Ownership model — single owner / shared / role-based / committee
• Delegation rules — who can transfer ownership and under what conditions
• Audit policy — what changes are logged, retained how long

If the substrate has compliance requirements (legal, regulatory, contractual), surface them explicitly here. Tier definitions should map cleanly to existing role/permission systems where possible — don't invent a new permission model unless the substrate's existing one is the problem being solved.

Composing phase-2-taxonomy-model.md

Combine the four streams into a single file at <working-dir>/phase-2-taxonomy-model.md. Structure:

# Phase 2 — Taxonomy Model

**Substrate:** <name>
**Date:** YYYY-MM-DD
**Preconditions:** Read substrate-context.md, phase-1-landscape-report.md
**Postconditions:** Ready for Phase 3 (system-environment-configuration)

## 1. Entity classes

[per-class definitions with examples and boundary cases]

## 2. Universal schema

[attributes that apply to all classes]

## 3. Class-specific schemas

[per-class attribute tables]

## 4. Relationships

[per-relationship cards + optional diagram]

## 5. Access framework

[per-class tier definitions, ownership, audit policy]

## 6. Open questions for Phase 3

[explicit list of decisions deferred to environment configuration —
e.g., "should `status` enum allow custom values per team, or be globally enumerated?"]

Gate criteria (auditor will check)

The model passes Phase 2's gate iff:

1. Entity classes are exhaustive and mutually exclusive — every asset from phase 1's inventory maps to exactly one class. If any are unclassifiable, declare a "Misc" class explicitly with a rule for when items belong there.
2. Universal schema has ≥ 3 attributes — at minimum: identity, ownership, lifecycle/state.
3. Every class-specific attribute has a type and required-ness — no schema fields with undefined types or undefined optionality.
4. Every relationship has a cardinality and a lifecycle coupling — no relationship cards missing those fields.
5. Every entity class has both visibility AND modification tiers declared — even if both default to "owner-only" or "public".
6. Open questions for Phase 3 section is present — even if empty.

Anti-patterns

• Don't import attribute schemas from frameworks you haven't chosen yet. Phase 3 picks the environment. Phase 2 is conceptual — it describes WHAT the taxonomy is, not WHICH database or CMS will hold it.
• Don't collapse entity classes prematurely. If two classes feel similar but have different lifecycles or different access tiers, they are different classes.
• Don't define attributes the substrate doesn't actually need. Every attribute is a validation cost. Only require what enforces invariants.
• Don't design access tiers that don't map to a real principal. Every tier must point to identifiable users, roles, or systems — not theoretical actors.

See also

• references/classification-strategies.md — common entity-classification patterns
• references/access-frameworks.md — visibility/modification tier patterns by domain