DMN diff

See what changed between two versions of a .dmn file as two decision requirements diagrams (DRDs) and their decision tables side by side, not as an XML diff.

Before on the left, after on the right. Pan and zoom in one pane and the other follows.

Open a diff

From Source Control. Click a modified .dmn file in the Source Control view, or open any Git diff of one (history, pull-request review). The left pane shows the old version, the right pane the new one.

Compare two files. In the Explorer:

• Select two .dmn files, right-click, Compare Selected (DMN). The first selected file is the before side.
• Or right-click one file, Select for Compare (DMN), then right-click the other, Compare with Selected (DMN). The pick is kept until you compare or reload the window.

File comparisons also show each file name above its pane and a ⇄ button that swaps the sides (its tooltip reads Swap sides).

If a Git diff still opens as XML, check workbench.diffEditorAssociations in your settings: a *.dmn entry there overrides the modeler.

Read the DRD

Both panes open on the DRD. Decisions, input data, business knowledge models, knowledge sources, text annotations and the requirements between them are highlighted:

Highlight	Shown in	Meaning
Green	After pane	Added
Red	Before pane	Removed
Blue	Both panes	Changed: a name or property, or the decision's table or expression
Dashed outline	Both panes	Moved: only the layout changed

In the after pane, a decision whose table changed carries a badge that counts the table's changes.

Read a decision table

Click the table icon of a decision to open its table; the other pane opens the same table. View DRD takes both panes back.

A rule removed on the left, a rule and an input column added on the right, a changed cell in blue and a moved rule with a striped number.

Highlight	Meaning
Green row or column	Added rule or input or output column
Red row or column	Removed rule or column
Blue cell	Changed entry or annotation; its rule number gets a blue bar
Blue column header	Changed label, expression or type
Striped rule number with ↕	Moved rule: same content, new position. Order decides a FIRST or PRIORITY table.
Blue hit policy	Changed table setting, such as the hit policy or its aggregation

The rule numbers stay in view while the table scrolls sideways. Scroll one table and the other follows to the same rule, even where rules were inserted or removed. A decision that exists in only one version shows Not in this version in the other pane, with a button back to the DRD. A changed literal expression or business knowledge model shows a coloured bar beside its expression.

Step through the changes

The legend above each pane counts the changes in the open view: the DRD, or the open table. Prev change and Next change step through them and move both panes together; the current change glows gold. In the DRD they go from top to bottom, then left to right; in a table, the table's settings first, then the columns, then the rules. A requirement or association that only moved along with its shapes is highlighted and counted, but not a step of its own. Both panes are read-only, but you can pan and zoom the DRD and scroll the tables.

The comparison follows element ids, as the BPMN diff does: a rule you copy and paste gets a new id and shows as removed and added. The colours are the BPMN diff's.

The DMN diff runs in VS Code. IntelliJ has no DMN editor yet.

Next steps

• BPMN diff: compare two versions of a process.
• Deployment: deploy the reviewed decisions.