Part 1 is here.* *

**strategy (n) **

*4. a plan, method, or series of maneuvers or stratagems for obtaining a specific goal or result: a strategy for getting ahead in the world.*

**goal (n)**

*1.the result or achievement toward which effort is directed; aim; end. *

**rule (n) **

*1. a principle or regulation governing conduct, action, procedure, arrangement, etc.: the rules of chess.*

An **extensive form game** is a specification of a game in game theory. This form represents the game as a tree. Each node (called a **decision node**) represents every possible state of play of the game as it is played. Play begins at a unique **initial node**, and flows through the tree along a path determined by the players until a **terminal node** is reached, where play ends and payoffs are assigned to all players. Each non-terminal node belongs to a player; that player chooses among the possible moves at that node, each possible move is an edge leading from that node to another node.

It should be noted that even in a game with a finite number of moves (steps) there are generally countless strategies (paths).

Looking at the Extensive Form diagram above and considering the definitions, we can see that the game above has two players: 1 and 2. The numbers by every non-terminal node indicate to which player that decision node belongs. The numbers by every terminal node represent the payoffs to the players (e.g. 2,1 represents a payoff of 2 to player 1 and a payoff of 1 to player 2). The labels by every edge of the graph are the name of the action that that edge represents.

I would like to play with the terminology. I would call the nodes “goals”, I would call the edges “rules” and the paths I would call “strategies”. Goals are actually states of the system and the rules are actually processes. Thinking about it this way makes me think of information architecture and website architecture. Browsing and navigation in this case becomes a one player strategy where the website provides the goals and rule set. However, the design process of the system is to determine the goal set and rule set of the player and provide a “natural” or even more optimal set of strategies for the user to follow.

Part 3 is here.