Lexical Structure

This page describes the tokens that make up the MDL language: keywords, literals, and identifiers.

Keywords

MDL keywords are case-insensitive. The following are reserved keywords:

ACCESS, ACTIONS, ADD, AFTER, ALL, ALTER, AND, ANNOTATION, AS, ASC,
ASCENDING, ASSOCIATION, AUTONUMBER, BATCH, BEFORE, BEGIN, BINARY,
BOOLEAN, BOTH, BUSINESS, BY, CALL, CANCEL, CAPTION, CASCADE,
CATALOG, CHANGE, CHILD, CLOSE, COLUMN, COMBOBOX, COMMIT, CONNECT,
CONFIGURATION, CONNECTOR, CONSTANT, CONSTRAINT, CONTAINER, CREATE,
CRUD, DATAGRID, DATAVIEW, DATE, DATETIME, DECLARE, DEFAULT, DELETE,
DELETE_BEHAVIOR, DELETE_BUT_KEEP_REFERENCES, DELETE_AND_REFERENCES, DEMO,
DEPTH, DESC, DESCENDING, DESCRIBE, DIFF, DISCONNECT, DROP, ELSE,
EMPTY, END, ENTITY, ENUMERATION, ERROR, EVENT, EVENTS, EXECUTE,
EXEC, EXIT, EXPORT, EXTENDS, EXTERNAL, FALSE, FOLDER, FOOTER,
FOR, FORMAT, FROM, FULL, GALLERY, GENERATE, GRANT, HEADER, HELP,
HOME, IF, IMPORT, IN, INDEX, INFO, INSERT, INTEGER, INTO, JAVA,
KEEP_REFERENCES, LABEL, LANGUAGE, LAYOUT, LAYOUTGRID, LEVEL, LIMIT,
LINK, LIST, LISTVIEW, LOCAL, LOG, LOGIN, LONG, LOOP, MANAGE, MAP,
MATRIX, MENU, MESSAGE, MICROFLOW, MICROFLOWS, MODEL, MODIFY, MODULE,
MODULES, MOVE, NANOFLOW, NANOFLOWS, NAVIGATION, NODE, NON_PERSISTENT,
NOT, NULL, OF, ON, OR, ORACLE, OVERVIEW, OWNER, PAGE, PAGES, PARENT,
PASSWORD, PERSISTENT, POSITION, POSTGRES, PRODUCTION, PROJECT,
PROTOTYPE, QUERY, QUIT, REFERENCE, REFERENCESET, REFRESH, REMOVE,
REPLACE, REPORT, RESPONSIVE, RETRIEVE, RETURN, REVOKE, ROLE, ROLES,
ROLLBACK, ROW, SAVE, SCRIPT, SEARCH, SECURITY, SELECTION, SET, SHOW,
SNIPPET, SNIPPETS, SQL, SQLSERVER, STATUS, STRING, STRUCTURE,
TABLES, TEXTBOX, TEXTAREA, THEN, TO, TRUE, TYPE, UNIQUE, UPDATE,
USER, VALIDATION, VALUE, VIEW, VIEWS, VISIBLE, WARNING, WHERE, WIDGET,
WIDGETS, WITH, WORKFLOWS, WRITE

Most keywords work unquoted as identifiers (entity names, attribute names). Only structural keywords like CREATE, DELETE, BEGIN, END, RETURN, ENTITY, and MODULE require quoting when used as identifiers.

Quoting escapes parser keywords only — not platform-reserved member names. Quoting an identifier tells the MDL parser to treat it as a name rather than a token, so "create", "status", and "type" parse fine as attribute names. But some names are reserved by the Mendix platform, and Studio Pro rejects them even when quoted (the quotes are stripped, and the bare name is still invalid): Type (CE7247), the audit attributes CreatedDate / ChangedDate / Owner / ChangedBy, plus ID, GUID, CurrentUser, and the Java keyword list. mxcli check --references flags these as MDL021 (CE7247) / MDL020. Rename them (e.g. Type → ResourceType); use the AutoCreatedDate / AutoChangedDate / AutoOwner / AutoChangedBy pseudo-types for the audit fields.

Literals

String Literals

String literals use single quotes:

'single quoted string'
'it''s here'            -- doubled single quote to escape

The only escape sequence is '' (two single quotes) to represent a literal single quote, as in a Mendix expression. Under mdl 1; a backslash is an ordinary character: 'C:\temp' is that path.

A string in a microflow or nanoflow expression is read by the same rule as any other string, and the expression stores its value the way Studio Pro does: an apostrophe doubled, a backslash and a line break as themselves. 'C:\temp' stores 'C:\temp', whether the builder renders the expression or stores it as written.

A string in an XPath constraint follows the same rule, wherever the XPath is written: a retrieve’s where, an entity access rule, a page datasource, a workflow user task’s targeting xpath, and a navigation sync constraint. So do the Mendix expressions a statement stores as written beside them — a retrieve’s limit and offset, a database query’s dynamic expression. describe writes each back as stored.

A line break is written into the literal itself: a string may span lines, and the break is part of its value. This is also how a text template — the message of log, show message or validation feedback — holds a line break; under mdl 1; a template written as one literal is the template text whether or not it spans lines:

mdl 1;
create microflow Shop.LogCleanup ($Count: Integer)
begin
  log info node 'Shop' 'Deleted {1} records.
Run again tomorrow.' with ({1} = toString($Count));
end;

describe writes every string this way — a caption, an annotation, a widget property, a string in an expression: '' is its only escape and a stored line break is a line break in the literal.

With with ({n} = …) parameters the literal is the template text too. Strings in a script without the header follow the older rules on Language Versions and Migration.

Numeric Literals

42          -- Integer
3.14        -- Decimal
-100        -- Negative integer
1.5e10      -- Scientific notation

Boolean Literals

TRUE
FALSE

Quoted Identifiers

When an identifier collides with a reserved keyword, use double quotes (ANSI SQL style) or backticks (MySQL style):

"ComboBox"."CategoryTreeVE"
`Order`.`Status`
"ComboBox".CategoryTreeVE    -- mixed quoting is allowed

See Qualified Names for more on identifier syntax and the Module.Name notation.

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