MDL Basics

MDL (Mendix Definition Language) is a SQL-like language for reading and modifying Mendix application projects. It provides a text-based alternative to the visual editors in Mendix Studio Pro.

What MDL Looks Like

MDL uses familiar SQL-style syntax with Mendix-specific extensions. Here is a simple example that creates an entity with attributes:

CREATE PERSISTENT ENTITY Sales.Customer (
  CustomerId: AutoNumber NOT NULL UNIQUE DEFAULT 1,
  Name: String(200) NOT NULL,
  Email: String(200) UNIQUE,
  IsActive: Boolean DEFAULT TRUE
)
INDEX (Name);

Statement Termination

Statements are terminated with a semicolon (;) or a forward slash (/) on its own line (Oracle-style, useful for multi-line statements):

-- Semicolon terminator
CREATE MODULE OrderManagement;

-- Forward-slash terminator (useful for long statements)
CREATE PERSISTENT ENTITY Sales.Order (
  OrderId: AutoNumber NOT NULL UNIQUE,
  OrderDate: DateTime NOT NULL
)
INDEX (OrderDate DESC);
/

Simple commands such as HELP, EXIT, STATUS, SHOW, and DESCRIBE do not require a terminator.

Case Insensitivity

All MDL keywords are case-insensitive. The following are equivalent:

CREATE PERSISTENT ENTITY Sales.Customer ( ... );
create persistent entity Sales.Customer ( ... );
Create Persistent Entity Sales.Customer ( ... );

Identifiers (module names, entity names, attribute names) are case-sensitive and must match the Mendix model exactly.

Statement Categories

MDL statements fall into several categories:

Further Reading

• Lexical Structure – keywords, literals, and tokens
• Qualified Names – how elements are referenced
• Comments – comment syntax
• Script Files – running MDL from files