A Framework for Searching AND/OR Graphs with Cycles
Ambuj Mahanti, Supriyo Ghose, Samir K. Sadhukhan

TL;DR
This paper introduces a comprehensive theoretical framework for searching cyclic AND/OR graphs, and presents two algorithms, S1 and S2, that effectively solve the problem with proven correctness and complexity analysis.
Contribution
It provides the first complete theoretical framework for cyclic AND/OR graph search and develops two new algorithms, S1 and S2, for uninformed and heuristically guided search.
Findings
Both S1 and S2 produce correct results in all tested cases.
S1 is a simple modification of the Bottom-up algorithm.
S2 extends Bottom-up with heuristics, replicating HS and AO* algorithms.
Abstract
Search in cyclic AND/OR graphs was traditionally known to be an unsolved problem. In the recent past several important studies have been reported in this domain. In this paper, we have taken a fresh look at the problem. First, a new and comprehensive theoretical framework for cyclic AND/OR graphs has been presented, which was found missing in the recent literature. Based on this framework, two best-first search algorithms, S1 and S2, have been developed. S1 does uninformed search and is a simple modification of the Bottom-up algorithm by Martelli and Montanari. S2 performs a heuristically guided search and replicates the modification in Bottom-up's successors, namely HS and AO*. Both S1 and S2 solve the problem of searching AND/OR graphs in presence of cycles. We then present a detailed analysis for the correctness and complexity results of S1 and S2, using the proposed framework. We…
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Taxonomy
TopicsOptimization and Search Problems · AI-based Problem Solving and Planning · Metaheuristic Optimization Algorithms Research
