generate-domain-model

name	generate-domain-model
description	Creating Mendix Domain Model MDL Scripts — entities, associations, enumerations, view entities, indexes, generalization, event handlers, ALTER ENTITY, positioning, and documentation
compatibility	opencode

MDL domain model author — generate well-documented, correctly positioned entity structures with associations, enumerations, and view entities.

> Full reference for generating Mendix domain model scripts. Covers modules, enumerations, persistent/non-persistent/view entities, indexes, generalization, auditing attributes, event handlers, associations, calculated attributes, ALTER ENTITY, and positioning guidelines.

Load when: - User asks to create a domain model for a specific use case - User wants to generate entities, associations, and enumerations - User requests a complete e-commerce, HR, CRM, or other business domain model - Needing ALTER ENTITY for incremental modifications

<critical_rules>

1. All CREATE statements MUST have JavaDoc-style documentation (/** ... */)
2. All entities MUST have @position(x, y) annotation
3. EXTENDS goes BEFORE the opening parenthesis — create persistent entity Module.Photo extends System.Image (...)
4. INDEX syntax goes AFTER the closing parenthesis, with NO comma before
5. Non-persistent entities cannot have validation rules (not null error, unique error) — only default values
6. Large files (300+ lines) MUST use -- MARK: Section Name comments (at least 3 for 300+ lines)
7. Always quote all identifiers with double quotes to avoid reserved keyword conflicts

</critical_rules>

<module_creation>

/**
 * Module for financial transaction management
 *
 * @since 1.0.0
 */
create module Finance;

</module_creation>

<mark_comments>

Use -- MARK: Section Name comments for navigation in large files:

-- MARK: ENUMERATIONS
-- MARK: CORE ENTITIES
-- MARK: - Core Entities (Persistent)
-- MARK: ASSOCIATIONS
-- MARK: VIEW ENTITIES
-- MARK: MICROFLOWS

</mark_comments>

/**
 * Transaction type classification
 *
 * @since 1.0.0
 */
create enumeration Module.TransactionType (
  INCOME 'Income',
  EXPENSE 'Expense'
);

Persistent Entity

/**
 * Entity description
 *
 * @since 1.0.0
 * @see Module.RelatedEntity
 */
@position(100, 100)
create persistent entity Module.EntityName (
  /** Unique identifier */
  Id: long not null error 'ID is required' unique error 'ID must be unique',
  /** Attribute description */
  attributename: string(200) not null error 'Attribute name is required',
  Amount: decimal,
  CreationDate: date,
  IsActive: boolean not null error 'IsActive flag is required' default true,
  status: enumeration(Module.StatusEnum) not null error 'Status is required'
);

Entity Indexes

INDEX syntax goes AFTER closing parenthesis, NO comma before first INDEX:

create persistent entity Module.Transaction (
  TransactionDate: datetime not null,
  status: enumeration(Module.Status) not null,
  Amount: decimal not null,
  IsRecurring: boolean default false
)
index (TransactionDate desc)
index (status, TransactionDate)
index (IsRecurring);

Entity Generalization (EXTENDS)

-- CORRECT: EXTENDS before (
create persistent entity Module.ProductPhoto extends System.Image (
  PhotoCaption: string(200),
  SortOrder: integer default 0
);

create persistent entity Module.Attachment extends System.FileDocument (
  AttachmentDescription: string(500)
);

-- WRONG: parse error
create persistent entity Module.Photo (PhotoCaption: string(200)) extends System.Image;

System Attributes (Auditing)

create persistent entity Sales.Order (
  OrderNumber: autonumber,
  TotalAmount: decimal not null,
  status: enumeration(Sales.OrderStatus) not null,
  owner: autoowner,
  ChangedBy: autochangedby,
  CreatedDate: autocreateddate,
  ChangedDate: autochangeddate
);

Pseudo-Type	System Attribute	Set When
autoowner	System.owner (→ System.User)	Object created
autochangedby	System.changedBy (→ System.User)	Every commit
autocreateddate	CreatedDate (DateTime)	Object created
autochangeddate	ChangedDate (DateTime)	Every commit

Non-Persistent Entity

Cannot have validation rules (not null error, unique error):

@position(200, 100)
create non-persistent entity Module.TemporaryData (
  SessionId: string(100),
  data: string(1000),
  IsActive: boolean default false
);

View Entity (with OQL)

@position(300, 500)
create view entity Module.ViewName (
  Attribute1: type,
  Attribute2: type
) as (
  select
    e.Id as Id,
    e.Name as Name,
    e.Amount as Amount
  from Module.Entity as e
  where e.IsActive = true
);

Enumeration Comparisons in OQL: Use the enumeration value (identifier), not the caption:

where e.Status != 'CANCELLED'   -- Correct: uses enum value
where e.Status != 'Cancelled'   -- Wrong: this is the caption

Entity Event Handlers

create persistent entity Sales.Order (
  Total: decimal,
  status: string(50)
)
on before commit call Sales.ACT_ValidateOrder raise error
on after create call Sales.ACT_InitDefaults;

-- Add via ALTER ENTITY
alter entity Sales.Order
  add event handler on before delete call Sales.ACT_CheckCanDelete raise error;

-- Drop via ALTER ENTITY
alter entity Sales.Order
  drop event handler on before commit;

Calculated Attributes

Only supported on persistent entities:

@position(100, 100)
create persistent entity Module.OrderLine (
  UnitPrice: decimal not null,
  Quantity: integer not null,
  TotalPrice: decimal calculated by Module.CalcTotalPrice
);

<data_types>

Type	Example	Description
string(length)	string(200)	Text field with max length
integer	integer	32-bit integer
long	long	64-bit integer (use for IDs)
decimal	decimal	Decimal number
boolean	boolean	True/false (auto-defaults to false)
datetime	datetime	Date and time
date	date	Date only
binary	binary	Binary data
autonumber	autonumber default 1	Auto-incrementing number
enumeration(Module.Enum)	enumeration(Shop.Status)	Enumeration reference

</data_types>

CRITICAL: Association Directionality

Associations are defined FROM the entity that contains the foreign key TO the entity that is referenced.

-- ✅ CORRECT: Transaction stores the account reference (foreign key)
create association Finance.Transaction_Account
from Finance.Transaction to Finance.Account
type reference;

-- ✅ One-to-Many: each order knows its customer
create association Sales.Order_Customer
from Sales.Order to Sales.Customer
type reference;

-- ✅ Many-to-Many
create association Sales.Order_Products
from Sales.Order to Sales.Product
type ReferenceSet
owner both;

-- ✅ Self-reference MUST use owner default (not owner both)
create association Module.Category_ParentCategory
from Module.Category to Module.Category
type reference
owner default;

Full Syntax:

/**
 * Association description
 *
 * @since 1.0.0
 */
create association Module.EntityWithFK_ReferencedEntity
from Module.EntityWithFK to Module.ReferencedEntity
type reference
owner default
delete_behavior DELETE_BUT_KEEP_REFERENCES
comment 'Additional documentation';

Delete Behaviors: DELETE_AND_REFERENCES, DELETE_BUT_KEEP_REFERENCES, DELETE_IF_NO_REFERENCES, cascade, prevent

Naming Convention: {FromEntity}_{ToEntity} (e.g., Order_Customer, Transaction_Account)

<alter_entity>

-- Add attribute
alter entity Module.Customer
  add attribute PhoneNumber: string(20);

-- Add multiple attributes
alter entity Module.Order
  add attribute VATRate: decimal
  add attribute VATAmount: decimal;

-- Rename attribute (preserves data)
alter entity Module.Order
  rename attribute CreatedDate to OrderDate;

-- Drop attribute
alter entity Module.Product
  drop attribute LegacyCode;

-- Modify attribute type
alter entity Module.Customer
  modify attribute Address: string(500);

-- Add index
alter entity Module.Customer
  add index idx_email (Email asc);

-- Reposition entity on domain model canvas
alter entity Module.Customer
  set position (100, 200);

Supported operations: ADD ATTRIBUTE, RENAME ATTRIBUTE, MODIFY ATTRIBUTE, DROP ATTRIBUTE, SET DOCUMENTATION, SET COMMENT, ADD INDEX, DROP INDEX, SET POSITION.

</alter_entity>

<entity_positioning>

Layout rules for readable domain models:

• Horizontal spacing: 350px between columns (x = 50, 400, 750, 1100, ...)
• Vertical spacing: calculate per-column: y = previous_y + 50 + (previous_entity_attribute_count * 20)
• Entity header is ~40px, each attribute adds ~20px of height, plus ~50px padding
• Place related entities in the same column or adjacent columns so associations are short

@position(50, 50)      -- Top-left: Core entity
create persistent entity Module.Customer (...);

@position(400, 50)     -- Same row: Related entity
create persistent entity Module.Address (...);

@position(50, 250)     -- Below: Dependent entity
create persistent entity Module.Order (...);

</entity_positioning>

<script_structure>

-- ============================================================================
-- Domain Model Name
-- ============================================================================

-- MARK: ENUMERATIONS

create enumeration Module.Enum1 (...);

-- MARK: CORE ENTITIES

-- MARK: - Entity Group 1

create persistent entity Module.Entity1 (...);

-- MARK: VIEW ENTITIES

create view entity Module.View1 as ...;

-- MARK: ASSOCIATIONS

create association Module.Assoc1 ...;

</script_structure>

• All entities have JavaDoc documentation
• All attributes have inline comments
• All associations have descriptions
• Position annotations on all entities
• MARK comments for files 300+ lines (at least 3 sections)
• All identifiers quoted with double quotes
• No duplicate names
• Valid OQL queries in view entities
• Required fields marked with NOT NULL (persistent entities only)
• Validation error messages added for NOT NULL and UNIQUE constraints
• IDs marked with NOT NULL UNIQUE
• Self-referencing associations use owner default
• EXTENDS before ( on generalization

<output_rules>Output MDL code only in code blocks. Keep explanations concise.</output_rules>