Extensive Form Settings Reference

Extensive Form Layout is a direct tree editor. Assignment supplies the available Players; Layout defines decisions, chance outcomes, terminal payoffs, and information sets.

Tree And Entry

The Tree selector changes the current Extensive Form module. The entry box above the first node is the tree label. The configured entry node is the first reachable decision, Nature, or Payoff node.

Click a node to select it. Decision nodes expose their Player selector; Nature nodes expose their label; Payoff nodes expose one formula per payoff recipient.

Toolbar

• Undo and Redo restore tree edits.
• Align tree recalculates automatic positions.
• Align payoffs places terminal payoff nodes on a common level where possible.
• Label payoff shows Player names beside terminal values.
• Zoom controls scale only the tree canvas from 50% to 160%; reset returns it to 100%.
• Player, Nature, and Payoff create a branch of the selected kind from the selected entry or branch-capable node.

The canvas keeps independent horizontal and vertical scrolling for large trees.

Player Decisions

A Player decision belongs to a Player defined under Assignment. Each outgoing branch has an editable Action name and a target node.

Adding a Player branch creates the Action, child decision, its first Action, and a terminal outcome as one structural operation. Adding a Payoff branch creates the Action and terminal node together. Newly created payoff formulas remain undefined until edited.

Nature Decisions

A Nature node contains named outcomes and probability or weight formulas. In the graphical edge label, enter the numeric expression first and then the outcome name, for example 0.5 Heads.

The editor can create a simple Nature branch ending in a Payoff, or a Nature decision branch leading to an independent Player decision. New probabilities and payoffs remain explicit rather than receiving hidden values.

Payoffs

A terminal Payoff node contains the ordered recipient vector used by the tree. Click a value to open the Formula editor.

Label payoff affects only the diagram display. It does not change recipients or values. After changing Assignment Players, inspect every terminal node because the editor synchronizes recipients where possible but cannot invent the intended formula.

Information Sets

An information set groups compatible Player decisions that the participant cannot distinguish.

Grouping requires the same Player and the same set of Action names. Select a compatible target and use the link command to group it with the current decision. The dashed line is a presentation of this shared information state, not a playable branch.

Within an information set, coordinated edits can add or remove equivalent:

• terminal Actions,
• one-step Player decisions,
• Nature outcomes,
• Nature outcomes followed by Player decisions.

The editor applies these changes atomically to every member. Dissolving an information set removes the grouping while preserving its existing branches.

Removal

The node removal control removes only structures whose ownership is unambiguous. Branch dialogs describe the exclusively referenced child structure that will also be removed. Shared or structurally ambiguous edits are refused instead of silently deleting reused nodes.

Review Order

1. Define Players in Assignment.
2. Build one complete path from entry to Payoff.
3. Add sibling Actions and Nature outcomes.
4. Group compatible decisions into information sets.
5. Complete every payoff formula.
6. Align and zoom the tree for inspection.
7. Run Validation.