Maria Fox and Derek Long
Highly symmetric problems result in redundant search effort which can render apparently simple problems intractable. Whilst the potential benefits of symmetry-breaking have been explored in the broader search and constraint satisfaction community there has been relatively little interest in the exploitation of this potential in planning. An initial exploration of the benefits of symmetry-breaking in a Graphplan framework, by Fox and Long in 1999 yielded promising results but failed to take into account the importance of identifying and exploiting new symmetries that arise during the search process. In this paper we extend the symmetry exploitation ideas described in Fox and Long (1999) to handle new symmetries and report results obtained from a range of planning problems.