DMN Master Support

• What is DMN Master?
• How do I start a model?
• How do I add and connect elements?
• How do I edit a decision table?
• What do the hit policy letters mean?
• Where do I change names and types?
• How do I select several elements?
• Keyboard shortcuts and the command palette
• What does the model check look for?
• Export, print and the XML source
• Where are my files stored?
• A file opens with a generated layout
• Will my file still open in other DMN tools?
• Can the app run my decisions?
• Settings and themes
• System requirements
• Contact and feedback

What is DMN Master?

An editor for decision models in DMN — Decision Model and Notation, the standard published by the Object Management Group. You draw the decision requirements diagram, describe each decision's logic in a decision table or an expression, and the app checks the model as you go. Everything is saved as a standard .dmn file — plain XML that other DMN tools can open. The app is written natively for Apple platforms: there is no web view inside it, and it needs no account and no internet connection.

How do I start a model?

Tap New decision model on the start screen on iPhone and iPad, or choose File → New on Mac. A new model holds one decision with an empty decision table. Select the decision and tap the “+” beside it to add the input data, sub-decisions or knowledge models it needs, already connected. To open an existing file, choose it in the document browser, in Files, or in Finder.

How do I add and connect elements?

The Library holds every element of a decision requirements diagram, drawn in real DMN notation, with a search field on top. On Mac and iPad it is the panel on the left; on iPhone, open it with the grid button at the end of the tool dock at the bottom of the screen.

• Tap an element in the library. If exactly one element is selected, the new one is placed beside it and connected to it with the requirement the notation allows — input data below a decision gets an information requirement, a knowledge model a knowledge requirement, a knowledge source an authority requirement.
• Drag an element from the library or the dock onto the canvas to put it exactly where you want. It is not connected to anything.
• Use the “+” beside a selected element: it offers only what can be connected to that element, and the new one lands where nothing else is drawn.

To connect two elements yourself, choose the Connect tool in the dock and drag from what is required to what requires it — from input data up to the decision that uses it. The app picks the right kind of requirement, and refuses connections the notation does not allow. A line to a text annotation becomes an association.

How do I edit a decision table?

Tap the small table icon in the top-left corner of a decision, or select the decision and press L. The logic opens in place of the canvas; Diagram (or ⌘↑) takes you back. A decision without logic offers Add decision table or Add literal expression.

• Cells are edited as in a spreadsheet: tap one and type. Every cell is a FEEL text field, Return moves down, and quotes stay straight so FEEL keeps working.
• The “+” in the table's header adds a rule, an input or an output.
• A rule number or a column header has a menu (right-click on Mac, touch and hold on iPhone and iPad) to insert, move or delete it; rules can also be duplicated.
• Selecting a column shows its label, expression, type, allowed values and default output in Properties.
• Columns resize by dragging their edge.

Literal expressions are edited in a monospaced editor together with their result type. Contexts, invocations, functions, relations, lists and the DMN 1.4 conditional, iteration and filter expressions are shown as boxed expressions, read-only.

What do the hit policy letters mean?

The letter in the top-left corner of a table is its hit policy: what happens when several rules match. Tap it to choose another; Properties shows the same choice as a grid that explains each one.

• U — Unique: rules must not overlap; exactly one may match.
• A — Any: rules may overlap, but every match must give the same output.
• P — Priority: the match whose output comes first in the allowed values wins.
• F — First: the first match in table order wins.
• R — Rule order: all matches, as a list in table order.
• O — Output order: all matches, sorted by the order of the allowed output values.
• C — Collect: all matches as a list, or combined by an aggregation: sum (C+), count (C#), minimum (C<) or maximum (C>).

Where do I change names, types and descriptions?

In Properties. On Mac and iPad it is the panel on the right; on iPhone, select an element and tap the properties button in the small bar above it. There you can edit an element's name and description, a decision's question and allowed answers, its variable type — FEEL's built-in types or the model's own item definitions — and a knowledge source's type. With nothing selected, Properties shows the model's name and namespace and the list of problems.

To rename, double-click or double-tap the element, or press Return. Renaming an element renames its variable too, as the specification requires.

How do I select several elements?

On Mac, Shift-click or Cmd-click to add to the selection, or drag from empty space to draw a selection rectangle; ⌘A selects everything. On iPhone and iPad, press and hold an element to add it to the selection. With several elements selected, Align and Distribute are in the “…” menu (and in the Arrange menu on Mac), next to Arrange automatically, which lays out the whole model.

Are there keyboard shortcuts?

Yes, on Mac and on iPad with a keyboard. ⌘K opens the command palette: one search field for every action, every element type to add and every element and decision table of the model to jump to. ⌘F finds elements by name.

Single letters pick tools (V select, H pan, C connect) and add elements (D decision, I input data, K knowledge model, S knowledge source, A annotation). With one element selected, the new one is placed below it as its requirement and connected — select a decision and type I I K to give it two inputs and a knowledge model. L opens the logic and F fits the model to the window. The full list is on the Keyboard page in Settings.

Where are undo and redo?

Undo is a button in the toolbar on every device, and redo is beside it or in the “…” menu, depending on how much room the toolbar has. With a keyboard, ⌘Z and ⇧⌘Z work as usual. Every edit can be undone, and typing in a field is one undo step, not one per letter.

What does the model check look for?

The model is checked as you edit: references to elements that do not exist, requirements the notation does not allow, cycles of information requirements, elements without a name, variables whose name differs from their element, decisions without logic, input data nothing uses and duplicate IDs. In decision tables it looks for tables with no rules, rules whose entries do not match the columns, outputs without names and aggregation with several outputs.

Errors get a red badge on the canvas and warnings an amber one. The badge at the top of the canvas counts them; tap it for the list, and tap an entry to jump to the element. Badges never appear in exports or printouts. To hide them, turn off Mark problems on the canvas in Settings → Editing.

How do I export, print or see the XML?

On Mac, click the Export button (the square with an arrow) in the toolbar; on iPhone and iPad, open Export in the “…” menu. Both offer Export as PNG, Export as PDF, Print and Show XML, which shows the file exactly as it will be saved, with syntax highlighting. On Mac, Print is also in the File menu (⌘P).

The PDF holds the whole model: the diagram on the first page and every decision table and expression on its own page after it. From an open decision table, export and print take just that table. Exports and printouts always use the light paper look, whichever theme you use on screen.

Where are my files stored?

Wherever you save them. DMN Master is a standard document-based app and uses the system file browser: Files on iPhone and iPad, Finder on Mac, including iCloud Drive and any other provider you have connected. On iPhone and iPad, the app's own folder is under Browse → On My iPhone (or iPad) → DMN Master. Plain .xml files that hold a DMN model open too.

On Mac, press Space on a .dmn file in Finder to preview it with Quick Look: the diagram and then every decision table, page by page.

A file opened with a generated layout. Why?

A DMN file can describe decisions without saying where anything is drawn — the layout lives in a separate DMNDI section, which DMN 1.1 did not have at all and which engines and scripts often leave out. DMN Master opens such a file with a layout of its own: input data at the bottom, each decision above what it requires, and the arrows pointing up, as in the specification. A note on the canvas says the layout was generated; saving writes it into the file.

Will my file still open in other DMN tools?

Yes. The app reads DMN 1.1 to 1.5 and saves each file in the version it was written in; new models are DMN 1.3, the version every common engine reads. The file is kept as a complete XML document and edited in place, never rewritten from scratch: item definitions, imports, extensions written by other DMN tools and the exact text of every expression survive a save untouched.

Can the app run my decisions?

No. DMN Master edits and checks decision models; it does not evaluate FEEL or execute decisions. Run the saved .dmn file in the decision engine you already use.

Where is Settings, and what is in it?

In the “…” toolbar menu on every device; on Mac you can also press ⌘, or choose DMN Master → Settings. It has five pages:

• General — appearance and interface language
• Canvas — dots or lines in the background, the minimap
• Editing — the buttons beside the selection, the model check
• Keyboard — every shortcut
• About — version, build and a link to the DMN specification

How do I change the theme?

In Settings → General → Appearance. Terracotta, the default, uses the colours of the app icon; Light is the bright paper look; Dark is espresso with cream lines. The change applies at once.

Can I change the language?

Yes. The app is available in English, German, French, Ukrainian, Spanish, Japanese and Portuguese. By default it follows your device language, falling back to English; you can change it in Settings → General, and it applies immediately without a restart.

Does it need an internet connection?

No. The app works entirely offline, makes no network requests and collects no data. See the Privacy Policy.

System requirements

iPhone with iOS 18 or later, iPad with iPadOS 18 or later, or a Mac with macOS 15 or later.