Hierarchical Influence Diagrams

Ledet, Thomas ; Kristensen, Michael Fogh

4. term

Computer Science, Master

2004

2012-02-14

This project report describes the Hierarchical Influence Diagrams (HID) framework for modeling a decision model for an agent in a game. A HID allows the designer to split a complex decision model consisting of a complex influence diagram, into a set of simpler ones and combine these as nodes in a tree structure. By doing so the agent only needs to consider information related to its current decision problem, since information is reduced when selecting an sub node and thereby traversing down the tree. When traversing down the HID, a leaf node is selected at the bottom, and this node decides the next HID decision which is the solution to the agents current decision problem. The HID framework offers the developer two choices of HID decision traversing; the event based algorithm and the time slot based algorithm. The event based algorithm reevaluates the previous selected HID leaf node if none of the information it was based has changed since the last HID decision. Otherwise it finds the first node where information has changed and makes a new traversal from this point. The time based algorithm reevaluates the previous traversing path starting from a specific node. This node is given from a user defined scheduling ratio which specifies the depth location of the next start node. A board-like real-time action game is designed for future test of the HID framework and thereby the test of the algorithms.

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