Eventmodeling Identifying Inputs

Identifying Inputs

Interview Phase (Optional)

When to Interview: Skip if the user has already identified UI actions/commands and processor triggers. Interview when it's unclear which actions are user-initiated vs. processor-automated.

Interview Strategy: Separate UI-driven commands from processor-driven commands before cataloging inputs. Mixing them leads to incorrect role attribution, which breaks the Role Catalog traceability that downstream steps depend on.

Critical Questions

1. Automation Level (Impact: Determines which commands are UI-triggered vs. processor-triggered)

• Question: "Are there actions that should be: (A) User-initiated only, (B) Processor-automated, (C) Mix of both?"
• Why it matters: Knowing automation vs. manual separates command types
• Follow-up triggers: If (C) → ask "Which specific user actions trigger automation? What does the processor decide on its own?"

1. External System Triggers (Impact: Determines if there are processor commands from webhooks/integrations)

• Question: "Will commands be triggered by: (A) UI only, (B) External webhooks (payments, notifications, etc.), (C) Scheduled processors, (D) All of above?"
• Why it matters: External triggers are processor commands, not UI commands
• Follow-up triggers: If (B) or (D) → ask which external systems send webhooks and what data they include

Interview Flow

Conditional Entry:

If user has provided:
  - UI actions already listed per storyboard screen
  - AND processor triggers identified with source systems named
  - AND it's clear which role/actor initiates each action

Then: Skip interview, proceed directly to command identification

Else: Conduct interview

Phase 1: Trigger Classification (Question 1)

• Establish which commands come from human actors vs. automated processors
• Confirm Role Catalog from Step 1 is available for attribution

Phase 2: External Triggers (Question 2)

• Identify all external system integrations that issue commands
• Confirm whether scheduled jobs or event-driven processors exist

Capturing Interview Findings

Append findings to the project's event modeling file:

File: .trogonai/interviews/[project-name]/EVENTMODELING.md

Use Write tool to add/update this section:

## 4. Identifying Inputs (eventmodeling-identifying-inputs)

### Automation Classification
[From Q1: Which actions are user-initiated vs. processor-automated?]

### External System Triggers
[From Q2: Which external systems trigger commands? Webhook formats?]

### Command Attribution Summary
- UI-issued commands: [list with role from Role Catalog]
- Processor-issued commands: [list with source system]

Update Interview Trail:

| 4 | eventmodeling-identifying-inputs | Done | UI commands, processor commands, role attribution |

---

Workflow

Given UI storyboards and event timeline, identify all inputs.

PREREQUISITE: The Role Catalog from Step 1 (eventmodeling-brainstorming-events) must exist. Every command identified below MUST be attributed to a specific role or system actor from that catalog.

1. Extract Commands from UI Actions

For each user action in storyboard, create a command attributed to a specific role:

Storyboard: Order Creation Screen
User action: Click "Create Order" button
  ↓
Command: CreateOrder
Input data from form:
    - customerId
    - items[] (product selections + quantities)
    - shippingAddress
Validation:
    - customerId must exist
    - items must not be empty
    - quantities must be > 0
Produces event: OrderCreated

2. Identify Processor Triggers

Identify automation-triggered commands:

Processor trigger: Payment gateway webhook received
  ↓
Command: AuthorizePayment (from Processor, not UI)
Input data from webhook:
    - orderId
    - paymentId
    - authorizationCode
Validation:
    - orderId must exist and be in Confirmed state
    - authorizationCode must be valid
Produces event: PaymentAuthorized

2b. Understand the Processor "Todo List" Pattern

Processors don't directly process events—they maintain a todo list driven by events:

Event Stream (Domain events):
PaymentAuthorized → triggers Inventory system

Processor: InventoryReserver

Todo List:
When PaymentAuthorized event arrives:
    1. Add item to todo: "Reserve inventory for order-123"

Processor Logic (continuously):
FOR EACH todo item IN todo_list:
    - Check if inventory available
    - If yes: Reserve inventory, produce InventoryReserved event, mark done
    - If no: Produce InventoryFailed event, mark failed
    - If error: Keep in todo for retry

Example:
Event: PaymentAuthorized(orderId=order-123, items=[{prodId: P1, qty: 2}])
    ↓
Todo added: Reserve P1 qty 2
    ↓
Processor checks: P1 has 5 available, need 2 
    ↓
Action: Reserve 2 units
    ↓
Event produced: InventoryReserved(orderId=order-123, reserved=[...])
    ↓
Todo marked done

Key insight: Processors are reactive. They listen for events and create todo items, then execute those todos by issuing commands that produce new events.

2c. Document Processor Automation (Gears Symbol)

Show which commands come from automation vs. user actions:

Command Catalog with Role Attribution (from Role Catalog):

UI-Issued Commands (attributed to specific human roles):
  1. CreateOrder (Order Entry screen) [ Customer]
  2. ConfirmOrder (Confirmation screen) [ Customer]
  3. CancelOrder (Status screen) [ Customer]
  4. RequestReturn (Order page) [ Customer]
  5. OverrideOrderStatus (Admin panel) [ Support Agent]

Processor-Issued Commands (attributed to system actors):
  6. AuthorizePayment (Payment gateway webhook) [ Payment Gateway]
  7. ReserveInventory (Triggered by PaymentAuthorized) [ Inventory System]
  8. CreateShipment (Triggered by InventoryReserved) [ Fulfillment System]
  9. NotifyCustomer (Triggered by multiple events) [ Notification Service]

Validation: Every command MUST have a role/actor attribution. If a command says [ User] instead of a specific role name, it's incomplete — go back to the Role Catalog and assign the correct role.

3. Document Command Specifics

For each command, define structure:

Command: ConfirmOrder
Source: UI (user clicks button)
Input:
    orderId: string (from URL/context)
    paymentMethod: enum ('card' | 'transfer')
    [paymentDetails]: depends on method

Validation rules:
    - Order must exist
    - Order must be in Draft state
    - Payment method must be supported
    - Funds must be available (pre-check)

Preconditions (from stream state):
    - OrderCreated event exists
    - No ConfirmOrder previously processed

Success result: OrderConfirmed event

Failure results:
    - "Order not found" → Command rejected, no event
    - "Order already confirmed" → Command rejected, no event
    - "Payment method not supported" → Command rejected, no event

4. Create Command Catalog

List all commands the system accepts:

Command Catalog: Order System

### UI-Issued Commands

1. CreateOrder
   Source: User (Order Entry screen)
   Input: customerId, items[], shippingAddress
   Produces: OrderCreated event

2. ConfirmOrder
   Source: User (Confirmation screen)
   Input: orderId, paymentMethod
   Produces: OrderConfirmed event

3. CancelOrder
   Source: User (Status screen)
   Input: orderId, reason
   Produces: OrderCancelled event

### Processor-Issued Commands

4. AuthorizePayment
   Source: Payment Processor (webhook)
   Input: orderId, paymentId, authCode
   Produces: PaymentAuthorized event

5. FailPayment
   Source: Payment Processor (webhook)
   Input: orderId, paymentId, reason
   Produces: PaymentFailed event

6. ReserveInventory
   Source: Inventory Processor (triggered by PaymentAuthorized)
   Input: orderId, items[]
   Produces: InventoryReserved event

7. CreateShipment
   Source: Fulfillment Processor (triggered by InventoryReserved)
   Input: orderId, items[]
   Produces: OrderShipped event

5. Map Data Sources

Document where each command input comes from:

Command: ConfirmOrder

Data origin matrix:
  orderId
    ↑ Source: UI context (from OrderCreated, displayed to user)
    ↑ Captured: Hidden in URL or session
    ↑ Validation: Must match Order from stream

  paymentMethod
    ↑ Source: UI form selection
    ↑ Captured: User selects checkbox/radio
    ↑ Validation: Must be in allowed list

[paymentDetails] (conditional)
    ↑ Source: Depends on paymentMethod
    ↑ For 'card': Card number, CVV, expiry (from payment form)
    ↑ For 'transfer': Bank account, routing number (from form)
    ↑ Validation: Format and validity checks

6. Identify Implicit Context

Document what comes from stream state:

Command: ShipOrder
Explicit input (from UI/Processor):
    orderId
    shipmentId (from fulfillment system)

Implicit context (from stream state):
    Order must exist
    Order must be in InventoryReserved state
    Payment must be authorized (from PaymentAuthorized event)
    Inventory must be reserved (from InventoryReserved event)

These implicit checks use stream state:
    currentState.orderId === orderId 
    currentState.status === 'InventoryReserved' 
    currentState.paymentId exists 
    currentState.shipmentId can be set 

Output Format

Present as:

# Inputs: [Domain Name]

## Commands Summary

| Command | Role/Actor | Source | Trigger | Input | Event |
|---------|------------|--------|---------|-------|-------|
| CreateOrder | Customer | UI | User action | customerId, items, address | OrderCreated |
| ConfirmOrder | Customer | UI | User action | orderId, paymentMethod | OrderConfirmed |
| CancelOrder | Customer | UI | User action | orderId, reason | OrderCancelled |
| AuthorizePayment | Payment Gateway | Processor | Webhook | orderId, paymentId | PaymentAuthorized |
| ReserveInventory | Inventory System | Processor | PaymentAuthorized event | orderId, items | InventoryReserved |
| ShipOrder | Fulfillment System | Processor | InventoryReserved event | orderId, shipmentId | OrderShipped |

---

## Detailed Commands

### Command: CreateOrder

**Source**: User (Order Entry screen)

**Input Data**:
- customerId: string
- items: Array
- shippingAddress: {street, city, state, zip}

**Validation**:
- customerId must exist in system
- items array must not be empty
- quantities must be > 0
- address fields must be non-empty

**Preconditions** (from stream state):
- Stream Order:X does not exist yet

**Success**: Produces OrderCreated event

**Failure**: Command rejected, no event
- "Customer not found"
- "Items invalid"
- "Address incomplete"

--- [Repeat for each command]

---

## Data Completeness Check

### Data Input → Event

Verify every command input becomes event data:

| Command Input | Event Data | Status |
|---------------|-----------|--------|
| customerId | orderId |  Stored in OrderCreated |
| items | items |  Stored in OrderCreated |
| shippingAddress | shippingAddress |  Stored in OrderCreated |

### Missing Data

Document any input that doesn't make it to events:
- None identified 

---

## Processor Commands

Document all processor-triggered commands:
[List each with source system and trigger condition]

Quality Checklist

• [ ] Every UI action maps to a command
• [ ] Every processor action maps to a command
• [ ] Every command is attributed to a specific role/actor from the Role Catalog
• [ ] No command uses generic "User" — must name the specific role (Customer, Seller, Admin, etc.)
• [ ] Every command input is documented
• [ ] Every input validates against rules
• [ ] Preconditions from stream state are explicit
• [ ] Success and failure outcomes documented
• [ ] Implicit context from stream state is identified
• [ ] No undocumented commands exist
• [ ] Command naming is consistent and clear
• [ ] Processor triggers are explicit
• [ ] Processor todo list pattern explained for each automation
• [ ] Event-to-todo triggering mechanism documented
• [ ] Automation marked with [AUTO] to distinguish from user actions [USER]
• [ ] Processor failure/retry handling specified

Key Principles

1. Source Clarity: Every command comes from UI or Processor
2. Input Completeness: All needed data captured
3. Validation Explicit: All rules documented
4. State Awareness: Preconditions from stream state clear
5. Event Mapping: Every input becomes event data

Common Patterns

User Command Pattern

User action on UI screen
  ↓
Captures form/selection data
  ↓
Validation checks
  ↓
Command issued
  ↓
Event created or rejection

Processor Command Pattern

External event/webhook received
  ↓
Triggers processor logic
  ↓
Processor validates and decides
  ↓
Command issued (if valid)
  ↓
Event created or decision recorded

Conditional Input Pattern

Command: PaymentConfirm
Input:
  - paymentMethod (user selected)
  - paymentDetails (conditional on method)
    If method='card': cardNumber, CVV, expiry
    If method='transfer': bankAccount, routingNumber

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: TrogonStack
• Source: TrogonStack/agentskills
• License: MIT

Install and usage instructions live in the source repository linked above.