Rodin Proving Perspective

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Overview

The Proving Perspective is made of a number of windows (views): the Proof Tree, the Goal, the Selected Hypotheses, the Proof Control, the Proof Information, and the Search Hypotheses. In subsequent sections, we study each of these windows. Below is a screenshot of the proving perspective:

Loading a Proof

In order to load a proof, switch to the Proving Perspective, select the project from the Event-B Explorer, select and expand the component (context or machine), finally select the proof obligation of interest. The corresponding proof will be loaded.

The Proof Tree

The proof tree describe each individual proof step in the proof. The proof tree can be seen in its corresponding window as seen in the following screenshot:

Each line in the tree corresponds to a node which is a sequent. A line is right shifted when the corresponding node is a direct descendant of the node of the previous line. Each node is labelled with a comment (description) explaining how it can be discharged. By selecting a node in the proof tree, the corresponding sequent is loaded: the hypotheses of the sequent are loaded to the Selected Hypotheses window, and the goal of the sequent is loaded to the Goal window.

Decoration

The leaves of the tree are decorated with three kinds of logos:

• a green logo with a "$\surd$" in it means that this leaf is discharged,
• a brown logo with a "?" in it means that this leaf is not discharged,
• a blue logo with a "R" in it means that this leaf has been reviewed.

Internal nodes in the proof tree are decorated in the same (but lighter) way. Note that a "reviewed" leaf is one that is not discharged yet by the prover. Instead, it has been "seen" by the user who decided to have it discharged later. Marking nodes as "reviewed" is very convenient in order to perform an interactive proof in a gradual fashion. In order to discharge a "reviewed" node, select it and prune the tree at that node: the node will become "brown" again (undischarged) and you can now try to discharge it.