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Proof Exploration

-- Author: Alexander Weigl, August 2021 valid for KeY-2.10.0


This note describes the Proof Exploration features in KeY-2.10. Proof Exploration allows a flexible editing of sequents, and therefore brings "What-If"-Analyses into KeY.

This feature is currently only available with --experimental flag.


We aggregrate under Proof Exploration, actions and views for supporting a What-If analysis. With the here described actions you can investigate the proof state and try to figure why a proof does not close. For this investigation, we offer following actions:

  • Add a formulae to the antecedent or succedent of a sequent.
  • Edit a formulae (or subterm) on a sequent
  • Delete formulae from the sequent

Proof Nodes, which are affected of exploration actions, are marked in the Proof Tree, accordingly.


Proof Exploration actions are only available if you activate the Exploration Mode in the toolbar.


  • AddFormulaToSuccedentAction
  • AddFormulaToAntecedentAction
  • DeleteFormulaAction
  • EditFormulaAction
  • ShowSecondBranchAction
  • ToggleExplorationAction


Image of Exploration Steps

Visualization of performed exploration actions. To jump to a node where the action was applied to select the entry in the list or the tree view. To prune exploration actions simply select an action and all action below this action (visible in the tree visualization) are removed.