EasyPlatform domain-analysis

Critical Thinking Mindset — Apply critical thinking, sequential thinking. Every claim needs traced proof, confidence >80% to act. Anti-hallucination: Never present guess as fact — cite sources for every claim, admit uncertainty freely, self-check output for errors, cross-reference independently, stay skeptical of own confidence — certainty without evidence root of all hallucination.

AI Mistake Prevention — Failure modes to avoid on every task:

• Check downstream references before deleting. Deleting components causes documentation and code staleness cascades. Map all referencing files before removal.
• Verify AI-generated content against actual code. AI hallucinates APIs, class names, and method signatures. Always grep to confirm existence before documenting or referencing.
• Trace full dependency chain after edits. Changing a definition misses downstream variables and consumers derived from it. Always trace the full chain.
• Trace ALL code paths when verifying correctness. Confirming code exists is not confirming it executes. Always trace early exits, error branches, and conditional skips — not just happy path.
• When debugging, ask "whose responsibility?" before fixing. Trace whether bug is in caller (wrong data) or callee (wrong handling). Fix at responsible layer — never patch symptom site.
• Assume existing values are intentional — ask WHY before changing. Before changing any constant, limit, flag, or pattern: read comments, check git blame, examine surrounding code.
• Verify ALL affected outputs, not just the first. Changes touching multiple stacks require verifying EVERY output. One green check is not all green checks.
• Holistic-first debugging — resist nearest-attention trap. When investigating any failure, list EVERY precondition first (config, env vars, DB names, endpoints, DI registrations, data preconditions), then verify each against evidence before forming any code-layer hypothesis.
• Surgical changes — apply the diff test. Bug fix: every changed line must trace directly to the bug. Don't restyle or improve adjacent code. Enhancement task: implement improvements AND announce them explicitly.
• Surface ambiguity before coding — don't pick silently. If request has multiple interpretations, present each with effort estimate and ask. Never assume all-records, file-based, or more complex path.

MANDATORY IMPORTANT MUST ATTENTION use

TaskCreate

AskUserQuestion

External Memory: For complex or lengthy work (research, analysis, scan, review), write intermediate findings and final results to a report file in

plans/reports/

— prevents context loss and serves as deliverable.

Evidence Gate: MANDATORY IMPORTANT MUST ATTENTION — every claim, finding, and recommendation requires

file:line

proof or traced evidence with confidence percentage (>80% to act, <80% must verify first).

Quick Summary

Goal: Analyze business domain: bounded contexts, aggregates, entities, VOs, domain events, cross-context relationships. Generate domain model report + ERD.

Workflow:

1. Load Business Context — Read idea, business evaluation, refined PBI artifacts + domain-entities-reference.md
2. Identify Bounded Contexts — Group related concepts, define context boundaries
3. Model Entities & Aggregates — Define aggregates, entities, value objects per context
4. Map Relationships — Entity relationships, cross-context integration points
5. Domain Events — Identify events crossing context boundaries
6. Generate ERD — Mermaid ER diagram with all entities and relationships
7. User Validation — Present model, ask 5-8 questions, confirm decisions
8. Domain Entity Change Assessment — Compare against domain-entities-reference.md, update if needed

Key Rules:

• MANDATORY IMPORTANT MUST ATTENTION validate every bounded context boundary with user
• MANDATORY IMPORTANT MUST ATTENTION include Mermaid ERD diagram in report
• MANDATORY IMPORTANT MUST ATTENTION run user validation interview at end (NEVER skip)
• Every entity belongs to exactly one bounded context
• Cross-context communication via domain events only — NEVER direct references

Be skeptical. Every claim needs traced proof, confidence percentages >80% to act.

DDD Reference: Strategic Design

Bounded Context Rules

Ubiquitous Language Rules:

• Every noun in codebase matches domain expert vocabulary exactly (not "User" when domain says "Employee")
• Class/method/variable names reflect ubiquitous language — zero translation layers inside bounded context
• Developers say "we call it X but domain means Y" → model is wrong, fix it

Context Map Pattern Decision Table

ACL — when to use: Upstream is external/legacy/third-party (Salesforce, SAP, Workday). Upstream types NEVER cross ACL into domain model.

Shared Kernel — when NOT to use: Teams cannot coordinate on every change → use Customer-Supplier + Published Language instead.

DDD Reference: Entity vs Value Object

Decision Matrix

Fast heuristics:

• Replace with equal-valued copy → breaks nothing? → Value Object
• Must be tracked across time or fetched by ID? → Entity
• Always retrieved as part of another object? → likely Value Object
• Two instances with same data are interchangeable? → Value Object

Canonical Value Objects

Money

Email

Address

DateRange

PhoneNumber

Percentage

Primitive Obsession → Value Object Mapping

string employeeId

EmployeeId

decimal amount, string currency

Money { amount, currency }

string street, string city, string zip

Address { ... }

DateTime start, DateTime end

DateRange { start, end }

string email

Email { value }

int percentage

Percentage { value }

string phoneNumber

PhoneNumber { countryCode, number }

Rule: Primitive with validation rules, formatting, or always passed grouped with other primitives → missing Value Object.

Value Object Construction Pattern

// Self-validating VO — never an invalid instance in memory
public sealed class Email : PlatformValueObject<Email>
{
    private Email(string value) { Value = value; }
    public string Value { get; }

    public static Email Of(string raw)
    {
        var normalized = raw?.Trim().ToLowerInvariant();
        if (string.IsNullOrWhiteSpace(normalized) || !IsValidFormat(normalized))
            throw new DomainException($"Invalid email: {raw}");
        return new Email(normalized);
    }
}

Rules:

• No public constructor without validation — factory method (

  Of()

  /

  Create()

  ) enforces invariants
• VOs can reference other VOs; VOs NEVER reference entities (lifecycle coupling)
• Mutation means replacement:

  email = Email.Of(newValue)

  , NEVER

  email.Value = newValue

VO Persistence Strategies

Rule: VOs NEVER have own table with primary key — that makes them entities by infrastructure.

DDD Reference: Entity Design

Identity Strategies

Rules:

• Prefer ULID for new entities — sortable, no coordination overhead
• NEVER use email/username as PK — users change them
• Cross-service references use same ID type as the owning service

Rich vs Anemic Domain Model

public set

EmployeeService.Activate(employee)

employee.Activate()

Tell Don't Ask Principle:

• BAD:

  if (employee.Status == Active) { employee.Status = Suspended; }

  (external ask + mutate)
• GOOD:

  employee.Suspend(reason)

  (entity enforces its own invariants)

Entity Invariant Enforcement

public class Employee : RootAuditedEntity<Employee, string, string>
{
    private Employee() { }  // ORM hydration only

    public static Employee Create(string name, Email email, DepartmentId departmentId)
    {
        Guard.NotNullOrWhitespace(name, nameof(name));
        Guard.NotNull(email, nameof(email));
        return new Employee
        {
            Id = Ulid.NewUlid().ToString(),
            Name = name,
            Email = email,
            DepartmentId = departmentId,
            Status = EmployeeStatus.Active
        };
    }

    public void Terminate(string reason, DateOnly terminationDate)
    {
        if (Status == EmployeeStatus.Terminated)
            throw new DomainException("Employee already terminated");
        if (terminationDate < DateOnly.FromDateTime(DateTime.UtcNow))
            throw new DomainException("Termination date cannot be in the past");

        Status = EmployeeStatus.Terminated;
        TerminationReason = reason;
        TerminationDate = terminationDate;
        AddDomainEvent(new EmployeeTerminatedDomainEvent(Id, terminationDate));
    }
}

Entity Lifecycle State Machines

Document ALL transitions explicitly. Unmodeled transitions throw

DomainException

Draft → Submitted (Submit())
Submitted → Approved (Approve(approverId))
Submitted → Rejected (Reject(reason))
Approved → Active (Activate())
Active → Suspended (Suspend(reason))
Suspended → Active (Reinstate())
Active → Archived (Archive())

Domain Validation Layers

Decision rule:

• Rule requires loading another aggregate? → Application service
• Rule needs only data within aggregate? → Entity method
• Rule concerns single value's format? → Value Object constructor

Factory Methods on Entities

Use when: construction requires domain logic, multiple paths, raises domain events, or object graph initialization.

Naming:

• Employee.Create(...)

  — primary creation

• Employee.Hire(...)

  — semantically loaded creation (domain language)
• Private constructor — ORM hydration only, NEVER called directly

Temporal (Bi-Temporal) Entities

Two time axes: valid time (fact true in real world) + transaction time (recorded in system).

EmployeeSalary {
    validFrom: DateOnly     // valid time: salary effective from
    validTo: DateOnly       // valid time: salary effective until
    recordedAt: DateTime    // transaction time: when entered into system
}

Use when: regulatory compliance, retroactive corrections, "as-of" queries.

DDD Reference: Aggregate Design

Aggregate Boundary Rules

1. Invariant scope — boundary = objects needed to enforce invariants atomically
2. Transaction boundary — exactly one database transaction per aggregate operation
3. Consistency scope — must be consistent atomically? same aggregate. Eventual consistency acceptable? separate aggregates
4. Small aggregates preferred — fewer members = fewer transaction conflicts = better scalability

Aggregate Size Heuristics

Aggregate Root Responsibilities

1. Maintain all invariants across all members
2. All mutation paths go through root (child entities NEVER directly accessible from outside)
3. Emit domain events for significant state changes
4. Control creation of child entities (factory methods on root)
5. Assign IDs to child entities

Rule: Outside code NEVER holds direct reference to non-root entity within aggregate.

Cross-Aggregate References

order.Customer.Name

CustomerId

Customer Customer

Aggregate Invariant Enforcement

public void AddLineItem(ProductId productId, int quantity, Money unitPrice)
{
    if (Status != OrderStatus.Draft)
        throw new DomainException("Cannot modify confirmed order");
    if (LineItems.Count >= 50)
        throw new DomainException("Order cannot exceed 50 line items");

    var item = OrderLineItem.Create(productId, quantity, unitPrice);
    _lineItems.Add(item);
    RecalculateTotal();  // invariant: Total == sum(lineItems)
}

Aggregate Design Patterns

When to Break Aggregate Rules (Pragmatic DDD)

Rule: Breaking aggregate rules acceptable ONLY when explicitly documented as technical debt with mitigation plan.

DDD Reference: ERD Design

Cardinality Types

|o--o|

|o--{

}o--o{

M:N rule: Relationship has attributes (date joined, role) → make join table explicit named entity.

1:1 decision: Same concept with optional attributes → same table. Different concepts with independent lifecycles → separate tables with FK.

Normalization Targets

Rule: 3NF for OLTP write models; denormalize only in read models/projections with documented justification.

Identifying vs Non-Identifying Relationships

Mapping to DDD: Identifying relationship → child entity inside parent aggregate. Non-identifying FK → likely separate aggregates.

ERD for Microservices

• Each bounded context has its OWN ERD — NEVER cross-service entity arrows
• Cross-service references shown as

  ExternalEntityId (string/ULID)

  — ID only, no relationship line
• Shared data shown as replicated/synced data note, NEVER shared table
• Event-sourced aggregates: ERD shows current state projection, not event stream

ERD Anti-Patterns

entityType + entityId

ERD to Aggregate Mapping

DDD Reference: Domain Events

Event Naming Conventions

Format:

{AggregateNoun}{PastTenseVerb}

EmployeeTerminated

TerminateEmployee

OrderConfirmed

OrderStatusChanged

PaymentProcessed

PaymentComplete

SalaryBandUpdated

SalaryChanged

Event Payload Design Rules

AggregateId

OccurredOn: DateTime (UTC)

Version

CorrelationId

Domain Events vs Integration Events

Rule: Domain event raised → in-process handlers fire → if cross-service needed, handler publishes integration event to message bus.

Event Versioning Strategies

OrderConfirmedV1

OrderConfirmedV2

Backward compatibility rules:

• Adding optional field → backward compatible
• Removing or renaming field → breaking
• Changing field type → breaking

DDD Reference: Repository Pattern

Interface Design Principles

1. One repository per aggregate root — NEVER one for child entities
2. Domain language in methods —

   GetActiveEmployeesInDepartment()

   not

   FindAll(e => e.Status == Active)

3. Return domain objects — repositories return entities, not DTOs
4. No infrastructure concerns — no

   IQueryable

   , no

   DbSet

   , no connection strings in interface
5. Async-first — all methods return

   Task<T>

   or

   IAsyncEnumerable<T>

Repository vs DAO

Query Objects — When to Use Specification

Use when: rule used in multiple places, warrants naming + testing, needs composition.

// Static expression on entity — composable, testable
public static Expression<Func<Employee, bool>> ByDepartmentExpression(string deptId)
    => e => e.DepartmentId == deptId && e.Status == EmployeeStatus.Active;

When NOT to use Specification: Simple single-use predicate → inline lambda. Rule only used once → repository method directly.

DDD Reference: Anti-Patterns Quick Reference

Terminate()

Approve()

Skill Workflow

Step 0: Locate Active Plan & Domain Reference (MANDATORY)

1. Glob

   plans/*/plan.md

   sorted by modification time — find active plan directory
2. Read

   plan.md

   — project scope, goals, prior decisions
3. Read all

   {plan-dir}/research/*.md

   — avoid duplicating prior work
4. Read

   docs/project-reference/domain-entities-reference.md

   (if exists) — project's single source of truth for domain entities (content auto-injected by hook — check for [Injected: ...] header before reading separately)
5. Set

   {plan-dir}

   variable — all outputs write to this directory

If no plan directory, create using naming convention from session context.

MUST ATTENTION update

{plan-dir}/plan.md

Step 1: Load Business Context

Read artifacts from prior workflow steps (search

plans/

team-artifacts/

• Active plan (

  {plan-dir}/plan.md

  ) — scope, goals, constraints
• Business evaluation report — value proposition, customer segments
• Refined PBI — acceptance criteria, user stories, features
• Discovery interview notes — problem statement, user roles

Extract and list:

• Nouns — Candidate entities (user, order, product, etc.)
• Verbs — Candidate domain events (created, approved, assigned, etc.)
• Roles — User types with different permissions/views
• Processes — Business workflows (application flow, review cycle, etc.)

Step 2: Identify Bounded Contexts

Group related entities using DDD principles. Apply context boundary signals from reference table above.

### Bounded Context: {Name}

**Purpose:** {What this context owns — one sentence}
**Classification:** Core domain / Supporting / Generic
**Key Responsibility:** {primary business capability}
**Team ownership:** {suggested team or role}
**Ubiquitous language:** {key terms and their meaning in this context}

Context boundary tests:

• Same term used by two teams with different meanings? → separate contexts
• Two entities with same name but different invariants? → separate contexts
• Can this context be worked on without understanding the other? → good separation

MANDATORY IMPORTANT MUST ATTENTION present identified contexts to user via

AskUserQuestion

• "I identified {N} bounded contexts: {list}. Does this grouping make sense?"
• Options: Agree (Recommended) | Merge {X} and {Y} | Split {Z} | Add missing context

Step 3: Model Entities & Aggregates

Per bounded context: classify each concept using Entity vs VO matrix above, then apply aggregate boundary rules.

### {Context Name}

**Aggregate Root:** {EntityName}
**Identity:** {ULID / UUID / Natural key — justify}
**Lifecycle states:** {Draft → Active → Archived, etc.}

- **Child Entities:** {list — share aggregate boundary, identifying FK}
- **Value Objects:** {list — immutable, no identity, embedded}
- **Invariants:** {business rules this aggregate enforces atomically}
- **Factory method:** {Employee.Create(...) / Employee.Hire(...)}

**Other Aggregates in this Context:**

- {Entity} — {purpose, identity strategy, lifecycle}

Entity Detail Template

VO Composition — MUST ATTENTION verify:

• 3+ primitives always travel together? → extract VO
• String field has format rules? → extract VO (Email, PhoneNumber)
• Numeric field has range rules? → extract VO (Percentage, Money)
• Concept named by domain experts but not modeled? → make explicit class

Aggregate Boundary — MUST ATTENTION verify:

• All entities in aggregate enforced in one transaction?
• Cross-aggregate references use ID only (no navigation properties)?
• Aggregate root is sole entry point for ALL mutations?
• Aggregate ≤ 5 entities? If not — justify or decompose

Step 4: Map Relationships

Intra-Context Relationships

| From | To        | Type | Cardinality     | Relationship Kind       | Description              |
| ---- | --------- | ---- | --------------- | ----------------------- | ------------------------ |
| Job  | Candidate | M:N  | via Application | Non-identifying (assoc) | Candidates apply to jobs |

Apply identifying vs non-identifying rule:

• Identifying relationship (child FK is part of PK) → child entity inside parent aggregate
• Non-identifying FK → likely separate aggregates

Cross-Context Integration (Context Map)

| Upstream Context | Downstream Context | Pattern | Integration Point          | Sync Mechanism |
| ---------------- | ------------------ | ------- | -------------------------- | -------------- |
| Recruitment      | Employee           | ACL     | Candidate becomes Employee | Domain event   |

Integration patterns to apply (see context map reference table above):

• Anti-Corruption Layer — external/hostile upstream model
• Customer-Supplier — downstream can negotiate with upstream
• Open Host Service — one upstream, many consumers
• Conformist — no negotiating power with upstream

Step 5: Domain Events

Identify events crossing bounded context boundaries. Apply naming:

{AggregateNoun}{PastTenseVerb}

CandidateHired

Event design — MUST ATTENTION verify:

• Name is past tense + includes aggregate noun?
• Payload includes AggregateId, OccurredOn (UTC), Version?
• Payload minimal — just what changed + correlation IDs?
• Version field included for schema evolution?
• Domain event vs integration event clearly classified?

Step 6: Generate ERD

Produce Mermaid ER diagram. Apply ERD-to-Aggregate mapping + anti-patterns from reference above.

```mermaid
erDiagram
    %% Bounded Context: {Name}
    ENTITY_A ||--o{ ENTITY_B : "has many"
    ENTITY_A {
        string id PK
        string name
        string status
        datetime createdAt
    }
    ENTITY_B {
        string id PK
        string entityAId FK
        string externalServiceId "ID only - no FK across services"
        string type
    }
```

ERD requirements:

• Group entities by bounded context (use Mermaid comments

  %% Context: ...

  )
• Show PK/FK fields and key business fields (not all fields)
• Show cardinality (1:1, 1:N, M:N) using Crow's Foot notation
• Cross-service references: string/ULID field with comment, no relationship line
• Identify association entities for M:N relationships

ERD — MUST ATTENTION verify before finalizing:

• No God tables (>20 columns — consider decomposing)?
• No cross-service FK arrows?
• All M:N through explicit named join entity?
• No nullable FK everywhere (clarify optional relationships)?

Step 7: User Validation Interview

MANDATORY IMPORTANT MUST ATTENTION present domain model and ask 5-8 questions via

AskUserQuestion

Required Questions

1. Context boundaries — "Are these {N} bounded contexts correct? Any missing or misplaced?"
   • Options: Correct (Recommended) | Need changes | Not sure, explain more
2. Aggregate roots — "Is {Entity} the right aggregate root for {Context}? It controls {child entities}."
3. Entity vs VO — "I modeled {concept} as a Value Object because it has no independent identity. Does that match the business model?"
4. Relationship verification — "The {Entity A} to {Entity B} relationship is {type/cardinality}. Is that correct?"
5. Missing entities — "Are there business concepts — workflows, roles, rules — I haven't captured as explicit domain objects?"
6. Event verification — "When {event} happens, should {contexts} be notified? What data do they need?"

Deep-Dive Questions (pick 2-3 based on complexity)

• "Should {Entity} be a separate aggregate or part of {Aggregate}? [separating = eventual consistency between them]"
• "Is {field} really a Value Object or does it need its own identity and lifecycle?"
• "How does {process} work step-by-step? What state transitions are involved?"
• "What happens when {edge case}? Which invariant prevents the bad state?"
• "Which entities change most frequently under concurrent load? (impacts aggregate design)"
• "Any concepts domain experts name that I haven't modeled explicitly?"

After user confirms, update report with final decisions and mark as

status: confirmed

Step 8: Domain Entity Change Assessment (MANDATORY)

MANDATORY IMPORTANT MUST ATTENTION compare domain analysis results against

docs/project-reference/domain-entities-reference.md

1. Identify new entities — in analysis but not in reference doc
2. Identify modified entities — changed fields, relationships, or bounded context assignment
3. Identify deprecated entities — in reference doc but no longer needed by feature
4. Present changes to user via

   AskUserQuestion

   :
   • "Domain entity changes detected: {N} new, {N} modified, {N} deprecated. Proceed with updating domain-entities-reference.md?"
   • Options: Approve all (Recommended) | Review each change | Skip update

If

docs/project-reference/domain-entities-reference.md

• "No domain-entities-reference.md found. Create it with all entities from this analysis?"
• Options: Yes, create it (Recommended) | No, skip

After user confirms: update/create

docs/project-reference/domain-entities-reference.md

Step 9: Update Main Plan (MANDATORY)

Read

{plan-dir}/plan.md

## Domain Model

## Domain Model

- **Bounded Contexts:** {N} — {list names with context map patterns between them}
- **Total Entities:** {N} ({N} aggregates, {N} child entities, {N} value objects)
- **Domain Events:** {N} cross-context events
- **Key Aggregates:** {list with invariant summaries}
- **Key Relationships:** {summary of critical relationships}
- **ERD:** See `phase-01-domain-model.md`
- **Full Analysis:** See `research/domain-analysis.md`

Output

{plan-dir}/research/domain-analysis.md          # Full domain analysis report
{plan-dir}/phase-01-domain-model.md             # Confirmed domain model with ERD
{plan-dir}/plan.md                              # Updated with domain model summary
docs/project-reference/domain-entities-reference.md  # Updated/created with new/modified entities

Report structure:

1. Executive summary (bounded contexts + entity count + key decisions)
2. Context map (bounded contexts with integration patterns)
3. Per-context entity/aggregate detail with identity strategy and invariants
4. Relationship tables (intra + cross-context, identifying vs non-identifying)
5. Value Objects catalog (VO type, attributes, invariants)
6. Domain events catalog (with payload design)
7. Mermaid ERD diagram
8. Anti-pattern warnings (any detected issues in model)
9. Unresolved questions

Report must be ≤250 lines. Use tables over prose.

MANDATORY IMPORTANT MUST ATTENTION break work into small todo tasks using

TaskCreate

AskUserQuestion

Next Steps

MANDATORY IMPORTANT MUST ATTENTION — NO EXCEPTIONS after completing this skill, use

AskUserQuestion

• "/review-domain-entities (Recommended)" — Review DDD quality of entities modeled/modified in this analysis (anemic model, VO classification, invariant enforcement, aggregate boundaries)
• "/tech-stack-research" — Research tech stack based on domain model
• "/plan" — If tech stack already decided and entity quality already reviewed
• "Skip, continue manually" — user decides

Closing Reminders

• MUST ATTENTION

  TaskCreate

  ALL tasks BEFORE starting — never begin without task breakdown

• MUST ATTENTION validate EVERY bounded context + key relationship with user via

  AskUserQuestion

  — never auto-decide

• MUST ATTENTION domain events ALWAYS follow

  {AggregateNoun}{PastTenseVerb}

  naming — NEVER command-style

• MUST ATTENTION NEVER have cross-service FK in ERD — ID reference + event-driven sync only

• MUST ATTENTION entity vs VO classification: replace with equal-valued copy breaks nothing? → VO. Else → Entity

• MUST ATTENTION add final review task to verify work quality

      <!-- SYNC:critical-thinking-mindset:reminder -->
  

• MUST ATTENTION apply critical thinking — every claim needs traced proof, confidence >80% to act. Anti-hallucination: never present guess as fact.

  <!-- /SYNC:critical-thinking-mindset:reminder --> <!-- SYNC:ai-mistake-prevention:reminder -->

• MUST ATTENTION apply AI mistake prevention — holistic-first debugging, fix at responsible layer, surface ambiguity before coding, re-read files after compaction.

  <!-- /SYNC:ai-mistake-prevention:reminder -->